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Difference between revisions of "Electrical Current"

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Line 13: Line 13:
 
===About Electrical Current===
 
===About Electrical Current===
 
: '''Current''' is [[measure]]d using an [[Ammeter]].
 
: '''Current''' is [[measure]]d using an [[Ammeter]].
−
: The [[SI Unit|units]] of '''current''' are [[Amp|amperes]], which are also called [[amp]]s ([[A]]).
+
: The [[SI Unit|units]] of '''current''' are [[Amp|amperes]], which are also called [[amp]]s (A).
−
: A '''current''' in a [[wire]] is a flow of [[electron]]s which are [[negative]]ly [[Electrical Charge|charge]]d [[particle]]s.
+
: A '''current''' in a [[wire]] is a flow of [[electron]]s which are [[Negative Charge|negative]]ly [[Electrical Charge|charge]]d [[particle]]s.
−
: Conventional '''Current''' flows from [[positive]] to [[negative]]. This is because [[electricity]] was discovered before [[scientist]]s knew about [[electron]]s.
+
: Conventional '''Current''' flows from positive to negative. This is because [[electricity]] was discovered before [[scientist]]s knew about [[electron]]s.
−
: In a [[salt]] [[solution]] '''current''' is the flow of both [[positive]] and [[negative]] [[ion]]s.
+
: In a [[salt]] [[solution]] '''current''' is the flow of both [[Positive Charge|positive]] and [[Negative Charge|negative]] [[ion]]s.
  
 
==Key Stage 4==
 
==Key Stage 4==
 
===Meaning===
 
===Meaning===
−
'''Electrical current''' is the [[rate]] of flow of [[Electrical Charge|charge]].
+
'''Electrical current''' is the rate of flow of [[Electrical Charge|charge]].
  
 
===About Electrical Current===
 
===About Electrical Current===
 
: '''Current''' is [[measure]]d using an [[Ammeter]].
 
: '''Current''' is [[measure]]d using an [[Ammeter]].
−
: The [[SI Unit]]s of '''current''' are [[Amp|amperes]], which are also called [[amp]]s ([[A]]).
+
: The [[SI Unit]]s of '''current''' are [[Amp|amperes]], which are also called [[amp]]s (A).
−
: A '''current''' in a [[wire]] is a flow of [[electron]]s which are [[negative]]ly [[Electrical Charge|charge]]d [[particle]]s.
+
: A '''current''' in a [[wire]] is a flow of [[electron]]s which are negatively [[Electrical Charge|charge]]d [[particle]]s.
−
: Conventional '''Current''' flows from [[positive]] to [[negative]]. This is because [[electricity]] was discovered before [[scientist]]s knew about [[electron]]s.
+
: Conventional '''Current''' flows from positive to negative. This is because [[electricity]] was discovered before [[scientist]]s knew about [[electron]]s.
−
: In a [[salt]] [[solution]] '''current''' is the flow of both [[positive]] and [[negative]] [[ion]]s.
+
: In a [[salt]] [[solution]] '''current''' is the flow of both [[Positive Charge|positive]] and [[Negative Charge|negative]] [[ion]]s.
 
: In a [[Series Circuit|series circuit]] the '''current''' is the same everywhere in the [[circuit]].
 
: In a [[Series Circuit|series circuit]] the '''current''' is the same everywhere in the [[circuit]].
 
: In a [[Parallel Circuit|parallel circuit]] the '''current''' splits at a [[junction]].
 
: In a [[Parallel Circuit|parallel circuit]] the '''current''' splits at a [[junction]].
Line 33: Line 33:
 
===Equation===
 
===Equation===
 
====Equation Linking Current, Charge and Time====
 
====Equation Linking Current, Charge and Time====
−
''NB: You should remember this equation.''
+
''NB: You should remember this equation with charge as the subject of the formula.''
  
 
'''Current''' = (Charge)/(time)
 
'''Current''' = (Charge)/(time)
Line 39: Line 39:
 
<math>I=\frac{Q}{t}</math>
 
<math>I=\frac{Q}{t}</math>
  
−
Where:
+
Where
  
 
<math>I</math> = The '''electrical current'''
 
<math>I</math> = The '''electrical current'''
Line 56: Line 56:
 
<math>I=\frac{V}{R}</math>
 
<math>I=\frac{V}{R}</math>
  
−
Where:
+
Where
  
 
<math>I</math> = The '''electrical current'''
 
<math>I</math> = The '''electrical current'''
Line 67: Line 67:
 
====Finding Current from Charge and Time====
 
====Finding Current from Charge and Time====
 
{| class="wikitable"
 
{| class="wikitable"
−
| style="height:20px; width:300px; text-align:center;" |A charge of 15 Coulombs passes through a point in a circuit ever 0.5 seconds. Calculate the current flowing past this point correct to two [[Significant Figures|significant figures]].
+
| style="height:20px; width:300px; text-align:center;" |A charge of 15 Coulombs passes through a point in a circuit ever 0.52 seconds. Calculate the current flowing past this point correct to two [[Significant Figures|significant figures]].
 
| style="height:20px; width:300px; text-align:center;" |A capacitor stores a charge of 10C. It discharges in 12ms. Calculate the current flowing out of the capacitor correct to two [[Significant Figures|significant figures]].
 
| style="height:20px; width:300px; text-align:center;" |A capacitor stores a charge of 10C. It discharges in 12ms. Calculate the current flowing out of the capacitor correct to two [[Significant Figures|significant figures]].
 
|-
 
|-
−
| style="height:20px; width:300px; text-align:left;" |'''1. State the known quantities'''
+
| style="height:20px; width:300px; text-align:left;" |'''1. State the known quantities in correct [[unit]]s.'''
  
 
Q = 15C
 
Q = 15C
  
−
t = 0.5s
+
t = 0.52s
−
| style="height:20px; width:300px; text-align:left;" |'''1. State the known quantities'''
+
| style="height:20px; width:300px; text-align:left;" |'''1. State the known quantities in correct [[unit]]s.'''
  
 
Q = 10C
 
Q = 10C
Line 85: Line 85:
 
<math>I=\frac{Q}{t}</math>
 
<math>I=\frac{Q}{t}</math>
  
−
<math>I=\frac{15}{0.5}</math>
+
<math>I=\frac{15}{0.52}</math>
  
−
<math>I=30A</math>
+
<math>I=28.846153A</math>
  
 +
<math>I\approx29A</math>
 
| style="height:20px; width:300px; text-align:left;" |'''2. [[Substitute (Maths)|Substitute]] the numbers into the [[equation]] and [[Solve (Maths)|solve]].'''
 
| style="height:20px; width:300px; text-align:left;" |'''2. [[Substitute (Maths)|Substitute]] the numbers into the [[equation]] and [[Solve (Maths)|solve]].'''
  
Line 102: Line 103:
 
====Finding Charge from Current and Time====
 
====Finding Charge from Current and Time====
 
{| class="wikitable"
 
{| class="wikitable"
−
| style="height:20px; width: 300px; text-align:center;" |A battery supplies 4Amps to a bulb over a period of 14 seconds. Calculate the charge leaving the battery in this time correct to two [[Significant Figures|significant figures]].
+
| style="height:20px; width: 300px; text-align:center;" |A battery supplies 4.7Amps to a bulb over a period of 14 seconds. Calculate the charge leaving the battery in this time correct to two [[Significant Figures|significant figures]].
−
| style="height:20px; width: 300px; text-align:center;" |A hairdryer uses a current of 7A for 5 minutes to dry a person’s hair. Calculate the charge flowing through the hairdryer in this time correct to two [[Significant Figures|significant figures]].
+
| style="height:20px; width: 300px; text-align:center;" |A hairdryer uses a current of 7.2A for 5 minutes to dry a person’s hair. Calculate the charge flowing through the hairdryer in this time correct to two [[Significant Figures|significant figures]].
 
|-
 
|-
−
| style="height:20px; width: 300px; text-align:left;" |'''1. State the known quantities'''
+
| style="height:20px; width: 300px; text-align:left;" |'''1. State the known quantities in correct [[unit]]s.'''
  
−
I = 4A
+
I = 4.7A
  
 
t = 14s
 
t = 14s
−
| style="height:20px; width: 300px; text-align:left;" |'''1. State the known quantities'''
+
| style="height:20px; width: 300px; text-align:left;" |'''1. State the known quantities in correct [[unit]]s.'''
  
−
I = 7A
+
I = 7.2A
  
 
t = 5min = 300s
 
t = 5min = 300s
Line 120: Line 121:
 
<math>I=\frac{Q}{t}</math>
 
<math>I=\frac{Q}{t}</math>
  
−
<math>4=\frac{Q}{14}</math>
+
<math>4.7=\frac{Q}{14}</math>
  
 
| style="height:20px; width: 300px; text-align:left;" |'''2. [[Substitute (Maths)|Substitute]] the numbers and [[Evaluate (Maths)|evaluate]].'''
 
| style="height:20px; width: 300px; text-align:left;" |'''2. [[Substitute (Maths)|Substitute]] the numbers and [[Evaluate (Maths)|evaluate]].'''
Line 126: Line 127:
 
<math>I=\frac{Q}{t}</math>
 
<math>I=\frac{Q}{t}</math>
  
−
<math>7=\frac{Q}{300}</math>
+
<math>7.2=\frac{Q}{300}</math>
  
 
|-
 
|-
 
| style="height:20px; width: 300px; text-align:left;" |'''3. [[Rearrange (Maths)|Rearrange]] the equation and [[Solve (Maths)|solve]].'''
 
| style="height:20px; width: 300px; text-align:left;" |'''3. [[Rearrange (Maths)|Rearrange]] the equation and [[Solve (Maths)|solve]].'''
  
−
<math>Q=4 \times 14</math>
+
<math>Q=4.7 \times 14</math>
  
−
<math>Q = 56C</math>
+
<math>Q = 65.8C</math>
  
 +
<math>Q \approx 66C</math>
 
| style="height:20px; width: 300px; text-align:left;" |'''3. [[Rearrange (Maths)|Rearrange]] the equation and [[Solve (Maths)|solve]].'''
 
| style="height:20px; width: 300px; text-align:left;" |'''3. [[Rearrange (Maths)|Rearrange]] the equation and [[Solve (Maths)|solve]].'''
  
−
<math>Q=7 \times 300</math>
+
<math>Q=7.2 \times 300</math>
 +
 
 +
<math>Q = 2160C</math>
  
−
<math>Q = 2100C</math>
+
<math>Q \approx 2200C</math>
 
|}
 
|}
  
 
====Finding Time from Current and Charge====
 
====Finding Time from Current and Charge====
 
{| class="wikitable"
 
{| class="wikitable"
−
| style="height:20px; width: 300px; text-align:center;" |A battery charger uses a current of 150mA to deliver a charge of 240 Coloumbs to a battery. Calculate the time taken to charge this battery correct to two [[Significant Figures|significant figures]].
+
| style="height:20px; width: 300px; text-align:center;" |A battery charger uses a current of 150mA to deliver a charge of 245 Coloumbs to a battery. Calculate the time taken to charge this battery correct to two [[Significant Figures|significant figures]].
−
| style="height:20px; width: 300px; text-align:center;" |A cloud in a thunderstorm loses 15kC in one lightening strike. At a current of 30,000kA. Calculate how long this lightning strike lasts correct to two [[Significant Figures|significant figures]].
+
| style="height:20px; width: 300px; text-align:center;" |A cloud in a thunderstorm loses 15C in one lightening strike. At a current of 31,000kA. Calculate how long this lightning strike lasts correct to two [[Significant Figures|significant figures]].
 
|-
 
|-
−
| style="height:20px; width: 300px; text-align:left;" |'''1. State the known quantities'''
+
| style="height:20px; width: 300px; text-align:left;" |'''1. State the known quantities in correct [[unit]]s.'''
  
 
I = 150mA = 150x10<sup>-3</sup>A
 
I = 150mA = 150x10<sup>-3</sup>A
  
−
Q = 240C
+
Q = 245C
−
| style="height:20px; width: 300px; text-align:left;" |'''1. State the known quantities'''
+
| style="height:20px; width: 300px; text-align:left;" |'''1. State the known quantities in correct [[unit]]s.'''
  
−
I = 30,000kA = 3x10<sup>7</sup>A
+
I = 31,000kA = 3.1x10<sup>7</sup>A
  
−
Q = 15kC = 15x10<sup>3</sup>
+
Q = 15C
 
|-
 
|-
 
| style="height:20px; width: 300px; text-align:left;" |'''2. [[Substitute (Maths)|Substitute]] the numbers and [[Evaluate (Maths)|evaluate]].'''
 
| style="height:20px; width: 300px; text-align:left;" |'''2. [[Substitute (Maths)|Substitute]] the numbers and [[Evaluate (Maths)|evaluate]].'''
Line 162: Line 166:
 
<math>I=\frac{Q}{t}</math>
 
<math>I=\frac{Q}{t}</math>
  
−
<math>150 \times 10^{-3} = \frac{240}{t}</math>
+
<math>150 \times 10^{-3} = \frac{245}{t}</math>
  
 
| style="height:20px; width: 300px; text-align:left;" |'''2. [[Substitute (Maths)|Substitute]] the numbers and [[Evaluate (Maths)|evaluate]].'''
 
| style="height:20px; width: 300px; text-align:left;" |'''2. [[Substitute (Maths)|Substitute]] the numbers and [[Evaluate (Maths)|evaluate]].'''
Line 168: Line 172:
 
<math>I=\frac{Q}{t}</math>
 
<math>I=\frac{Q}{t}</math>
  
−
<math>3 \times 10^7 = \frac{15 \times 10^3}{t}</math>
+
<math>3.1 \times 10^7 = \frac{15}{t}</math>
 
|-
 
|-
 
| style="height:20px; width: 300px; text-align:left;" |'''3. [[Rearrange (Maths)|Rearrange]] the equation and [[Solve (Maths)|solve]].'''
 
| style="height:20px; width: 300px; text-align:left;" |'''3. [[Rearrange (Maths)|Rearrange]] the equation and [[Solve (Maths)|solve]].'''
  
−
<math>t=\frac{240}{150 \times 10^{-3}}</math>
+
<math>t=\frac{245}{150 \times 10^{-3}}</math>
  
−
<math>t=1600s</math>
+
<math>t=1633.3s</math>
  
 +
<math>t\approx1633.3s</math>
 
| style="height:20px; width: 300px; text-align:left;" |'''3. [[Rearrange (Maths)|Rearrange]] the equation and [[Solve (Maths)|solve]].'''
 
| style="height:20px; width: 300px; text-align:left;" |'''3. [[Rearrange (Maths)|Rearrange]] the equation and [[Solve (Maths)|solve]].'''
  
−
<math>t=\frac{15 \times 10^3}{3 \times 10^7}</math>
+
<math>t=\frac{15}{3.1 \times 10^7}</math>
 +
 
 +
<math>t = 4.8387 \times 10^{-7}s</math>
  
−
<math>t = 5.0 \times 10^{-4}s</math>
+
<math>t\approx4.8 \times 10^{-7}s</math>
 
|}
 
|}
  
 
====Finding Current from Potential Difference and Resistance====
 
====Finding Current from Potential Difference and Resistance====
 
{| class="wikitable"
 
{| class="wikitable"
−
| style="height:20px; width:300px; text-align:center;" |A [[Potential Difference|potential difference]] of 9.9V is placed across an 18 Ohm [[Electrical Resistor|resistor]]. Calculate the '''current''' flowing through the [[Electrical Resistor|resistor]] correct to two [[Significant Figures|significant figures]].
+
| style="height:20px; width:300px; text-align:center;" |A [[Potential Difference|potential difference]] of 9.9V is placed across an 19 Ohm [[Electrical Resistor|resistor]]. Calculate the '''current''' flowing through the [[Electrical Resistor|resistor]] correct to two [[Significant Figures|significant figures]].
 
| style="height:20px; width:300px; text-align:center;" |A toaster has a [[Electrical Resistance|resistance]] of 27 Ohms is plugged into the [[Mains Electricity|mains]] which has a [[Potential Difference|potential difference]] of 230V. Calculate the current flowing through the toaster correct to two [[Significant Figures|significant figures]].
 
| style="height:20px; width:300px; text-align:center;" |A toaster has a [[Electrical Resistance|resistance]] of 27 Ohms is plugged into the [[Mains Electricity|mains]] which has a [[Potential Difference|potential difference]] of 230V. Calculate the current flowing through the toaster correct to two [[Significant Figures|significant figures]].
 
|-
 
|-
−
| style="height:20px; width:300px; text-align:left;" |'''1. State the known quantities'''
+
| style="height:20px; width:300px; text-align:left;" |'''1. State the known quantities in correct [[unit]]s.'''
  
 
V = 9.9V
 
V = 9.9V
  
−
R = 18Ω
+
R = 19Ω
−
| style="height:20px; width:300px; text-align:left;" |'''1. State the known quantities'''
+
| style="height:20px; width:300px; text-align:left;" |'''1. State the known quantities in correct [[unit]]s.'''
−
 
 
 
V = 230V
 
V = 230V
  
Line 203: Line 209:
 
<math>I=\frac{V}{R}</math>
 
<math>I=\frac{V}{R}</math>
  
−
<math>I=\frac{9.9}{18}</math>
+
<math>I=\frac{9.9}{19}</math>
  
−
<math>I=0.55A</math>
+
<math>I=0.52105A</math>
  
 +
<math>I\approx0.52A</math>
 
| style="height:20px; width:300px; text-align:left;" |'''2. [[Substitute (Maths)|Substitute]] the numbers into the [[equation]] and [[Solve (Maths)|solve]].'''
 
| style="height:20px; width:300px; text-align:left;" |'''2. [[Substitute (Maths)|Substitute]] the numbers into the [[equation]] and [[Solve (Maths)|solve]].'''
  
Line 217: Line 224:
 
<math>I\approx8.5A</math>
 
<math>I\approx8.5A</math>
 
|}
 
|}
 +
 +
====Finding Resistance from Potential Difference and Current====
 +
{| class="wikitable"
 +
| style="height:20px; width: 300px; text-align:center;" |A student measures a [[Potential Difference|potential difference]] of 5.4V and a current of 0.13mA across a component. Calculate the [[Electrical Resistance|resistance]] of the [[Electrical Component|component]].
 +
| style="height:20px; width: 300px; text-align:center;" |Calculating the [[Electrical Resistance|resistance]] of a [[buzzer]] connected in series to a 9V battery with an [[ammeter]] reading of 23mA.
 +
|-
 +
| style="height:20px; width: 300px; text-align:left;" |'''1. State the known quantities in correct [[unit]]s.'''
 +
 +
V = 5.4V
 +
 +
I = 0.13mA = 0.13x10<sup>-3</sup>
 +
| style="height:20px; width: 300px; text-align:left;" |'''1. State the known quantities in correct [[unit]]s.'''
 +
V = 9V
 +
 +
I = 23mA = 23x10<sup>-3</sup>
 +
|-
 +
| style="height:20px; width: 300px; text-align:left;" |'''2. [[Substitute (Maths)|Substitute]] the numbers and [[Evaluate (Maths)|evaluate]].'''
 +
 +
<math>I=\frac{V}{R}</math>
 +
 +
<math>0.13 \times 10^{-3}=\frac{5.4}{R}</math>
 +
 +
| style="height:20px; width: 300px; text-align:left;" |'''2. [[Substitute (Maths)|Substitute]] the numbers and [[Evaluate (Maths)|evaluate]].'''
 +
 +
<math>23 \times 10^{-3}=\frac{9}{R}</math>
 +
|-
 +
| style="height:20px; width: 300px; text-align:left;" |'''3. [[Rearrange (Maths)|Rearrange]] the equation and [[Solve (Maths)|solve]].'''
 +
 +
<math>R=\frac{5.4}{0.13 \times 10^{-3}}</math>
 +
 +
<math>R=41538.46\Omega</math>
 +
 +
<math>R\approx 42000\Omega</math>
 +
 +
| style="height:20px; width: 300px; text-align:left;" |'''3. [[Rearrange (Maths)|Rearrange]] the equation and [[Solve (Maths)|solve]].'''
 +
 +
<math>R=\frac{9}{23 \times 10^{-3}}</math>
 +
 +
<math>R=391.3043\Omega</math>
 +
 +
<math>R\approx 390\Omega</math>
 +
|}
 +
 +
====Finding Potential Difference from Current and Resistance====
 +
{| class="wikitable"
 +
| style="height:20px; width: 300px; text-align:center;" |A '''current''' of 55mA flows through a [[Electrical Component|component]] with a [[Electrical Resistance|resistance]] of 93 Ohms. Calculate the [[Potential Difference|potential difference]] across this [[Electrical Component|component]] correct to two [[Significant Figures|significant figures]].
 +
| style="height:20px; width: 300px; text-align:center;" |A 22kΩ [[Electrical Resistor|resistor]] has a '''current''' flowing through it of 6mA. Calculate the [[Potential Difference|potential difference]] across the [[Electrical Resistor|resistor]] correct to two [[Significant Figures|significant figures]].
 +
|-
 +
| style="height:20px; width: 300px; text-align:left;" |'''1. State the known quantities in correct [[unit]]s.'''
 +
 +
I = 55mA = 55x10<sup>-3</sup>A
 +
 +
R = 93Ω
 +
| style="height:20px; width: 300px; text-align:left;" |'''1. State the known quantities in correct [[unit]]s.'''
 +
 +
I = 6mA = 6x10<sup>-3</sup>A
 +
 +
R = 22kΩ = 22x10<sup>3</sup>Ω
 +
|-
 +
| style="height:20px; width: 300px; text-align:left;" |'''2. [[Substitute (Maths)|Substitute]] the numbers and [[Evaluate (Maths)|evaluate]].'''
 +
 +
<math>I=\frac{V}{R}</math>
 +
 +
<math>55 \times 10^{-3}=\frac{V}{93}</math>
 +
| style="height:20px; width: 300px; text-align:left;" |'''2. [[Substitute (Maths)|Substitute]] the numbers and [[Evaluate (Maths)|evaluate]].'''
 +
 +
<math>I=\frac{V}{R}</math>
 +
 +
<math>6 \times 10^{-3}=\frac{V}{22 \times 10^3}</math>
 +
|-
 +
| style="height:20px; width: 300px; text-align:left;" |'''3. [[Rearrange (Maths)|Rearrange]] the equation and [[Solve (Maths)|solve]].'''
 +
 +
<math>V= 55 \times 10^{-3} \times 93</math>
 +
 +
<math>V= 5.115V</math>
 +
 +
<math>V\approx5.1V</math>
 +
 +
| style="height:20px; width: 300px; text-align:left;" |'''3. [[Rearrange (Maths)|Rearrange]] the equation and [[Solve (Maths)|solve]].'''
 +
 +
<math>V= 6 \times 10^{-3} \times 22 \times 10^3</math>
 +
 +
<math>V= 132V</math>
 +
 +
<math>V\approx130V</math>
 +
|}
 +
 +
 +
===References===
 +
====AQA====
 +
 +
:[https://www.amazon.co.uk/gp/product/1782945598/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1782945598&linkCode=as2&tag=nrjc-21&linkId=ad276ad49df77ab4b40ab4fd0fe09817 ''Current (electrical), pages 180, 181, 190, GCSE Combined Science; The Revision Guide, CGP, AQA '']
 +
:[https://www.amazon.co.uk/gp/product/178294558X/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=178294558X&linkCode=as2&tag=nrjc-21&linkId=f0dfb66dafcb0c6e9449e7b1a4ae1ac76 ''Current (electrical), pages 24, 33, GCSE Physics; The Revision Guide, CGP, AQA '']
 +
:[https://www.amazon.co.uk/gp/product/1782945598/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1782945598&linkCode=as2&tag=nrjc-21&linkId=ad276ad49df77ab4b40ab4fd0fe09818 ''Current (electrical); alternating, page 188, GCSE Combined Science; The Revision Guide, CGP, AQA '']
 +
:[https://www.amazon.co.uk/gp/product/178294558X/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=178294558X&linkCode=as2&tag=nrjc-21&linkId=f0dfb66dafcb0c6e9449e7b1a4ae1ac77 ''Current (electrical); alternating, pages 31, 96, 97, GCSE Physics; The Revision Guide, CGP, AQA '']
 +
:[https://www.amazon.co.uk/gp/product/1782945598/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1782945598&linkCode=as2&tag=nrjc-21&linkId=ad276ad49df77ab4b40ab4fd0fe09819 ''Current (electrical); direct, page 188, GCSE Combined Science; The Revision Guide, CGP, AQA '']
 +
:[https://www.amazon.co.uk/gp/product/178294558X/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=178294558X&linkCode=as2&tag=nrjc-21&linkId=f0dfb66dafcb0c6e9449e7b1a4ae1ac78 ''Current (electrical); direct, pages 31, 97, GCSE Physics; The Revision Guide, CGP, AQA '']
 +
:[https://www.amazon.co.uk/gp/product/1782945598/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1782945598&linkCode=as2&tag=nrjc-21&linkId=ad276ad49df77ab4b40ab4fd0fe09820 ''Current (electrical); energy transferred, page 190, GCSE Combined Science; The Revision Guide, CGP, AQA '']
 +
:[https://www.amazon.co.uk/gp/product/1782945598/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1782945598&linkCode=as2&tag=nrjc-21&linkId=ad276ad49df77ab4b40ab4fd0fe09821 ''Current (electrical); I-V characteristics, page 183, GCSE Combined Science; The Revision Guide, CGP, AQA '']
 +
:[https://www.amazon.co.uk/gp/product/178294558X/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=178294558X&linkCode=as2&tag=nrjc-21&linkId=f0dfb66dafcb0c6e9449e7b1a4ae1ac79 ''Current (electrical); I-V characteristics, page 26, GCSE Physics; The Revision Guide, CGP, AQA '']
 +
:[https://www.amazon.co.uk/gp/product/1782945598/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1782945598&linkCode=as2&tag=nrjc-21&linkId=ad276ad49df77ab4b40ab4fd0fe09823 ''Current (electrical); magnetic field around a current-carrying wire, page 230, GCSE Combined Science; The Revision Guide, CGP, AQA '']
 +
:[https://www.amazon.co.uk/gp/product/178294558X/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=178294558X&linkCode=as2&tag=nrjc-21&linkId=f0dfb66dafcb0c6e9449e7b1a4ae1ac80 ''Current (electrical); magnetic field around a current-carrying wire, pages 93, 94, GCSE Physics; The Revision Guide, CGP, AQA '']
 +
:[https://www.amazon.co.uk/gp/product/1782945598/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1782945598&linkCode=as2&tag=nrjc-21&linkId=ad276ad49df77ab4b40ab4fd0fe09822 ''Current (electrical); mains supply, page 188, GCSE Combined Science; The Revision Guide, CGP, AQA '']
 +
:[https://www.amazon.co.uk/gp/product/1782945598/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1782945598&linkCode=as2&tag=nrjc-21&linkId=ad276ad49df77ab4b40ab4fd0fe09824 ''Current (electrical); national grid, page 191, GCSE Combined Science; The Revision Guide, CGP, AQA '']
 +
:[https://www.amazon.co.uk/gp/product/1782945598/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1782945598&linkCode=as2&tag=nrjc-21&linkId=ad276ad49df77ab4b40ab4fd0fe09825 ''Current (electrical); parallel circuits, pages 186-187, GCSE Combined Science; The Revision Guide, CGP, AQA '']
 +
:[https://www.amazon.co.uk/gp/product/1782945598/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1782945598&linkCode=as2&tag=nrjc-21&linkId=ad276ad49df77ab4b40ab4fd0fe09826 ''Current (electrical); series circuits, pages 185-187, GCSE Combined Science; The Revision Guide, CGP, AQA '']
 +
:[https://www.amazon.co.uk/gp/product/0008158770/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=0008158770&linkCode=as2&tag=nrjc-21&linkId=ec31595e720e1529e49876c3866fff6e ''Current, pages 46-7, 52-69, 72-5, 247-9, GCSE Physics; Student Book, Collins, AQA '']
 +
:[https://www.amazon.co.uk/gp/product/019835939X/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=019835939X&linkCode=as2&tag=nrjc-21&linkId=57e96876985fc39b1a3d8a3e3dc238b6 ''Current, pages 52-53, 58-61, 64-65, 68-71, 216-229, GCSE Physics; Third Edition, Oxford University Press, AQA '']
 +
:[https://www.amazon.co.uk/gp/product/1782946403/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1782946403&linkCode=as2&tag=nrjc-21&linkId=32a0abb60dff015b15b50e9b1d7b4644 ''Current, pages 61-67, GCSE Combined Science Trilogy; Physics, CGP, AQA '']
 +
:[https://www.amazon.co.uk/gp/product/1782945970/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1782945970&linkCode=as2&tag=nrjc-21&linkId=a120d24dcc7cc7a58192069a3aafc1d2 ''Current, pages 63-69, GCSE Physics; The Complete 9-1 Course for AQA, CGP, AQA '']
 +
:[https://www.amazon.co.uk/gp/product/1782946403/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1782946403&linkCode=as2&tag=nrjc-21&linkId=32a0abb60dff015b15b50e9b1d7b4644 ''Current; alternating (ac), pages 86, 203, GCSE Combined Science Trilogy; Physics, CGP, AQA '']
 +
:[https://www.amazon.co.uk/gp/product/1782945970/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1782945970&linkCode=as2&tag=nrjc-21&linkId=a120d24dcc7cc7a58192069a3aafc1d2 ''Current; alternating (ac), pages 89, 245, 306, GCSE Physics; The Complete 9-1 Course for AQA, CGP, AQA '']
 +
:[https://www.amazon.co.uk/gp/product/1782946403/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1782946403&linkCode=as2&tag=nrjc-21&linkId=32a0abb60dff015b15b50e9b1d7b4644 ''Current; direct (dc), page 86, GCSE Combined Science Trilogy; Physics, CGP, AQA '']
 +
:[https://www.amazon.co.uk/gp/product/1782945970/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1782945970&linkCode=as2&tag=nrjc-21&linkId=a120d24dcc7cc7a58192069a3aafc1d2 ''Current; direct (dc), pages 89, 306, GCSE Physics; The Complete 9-1 Course for AQA, CGP, AQA '']
 +
:[https://www.amazon.co.uk/gp/product/1782946403/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1782946403&linkCode=as2&tag=nrjc-21&linkId=32a0abb60dff015b15b50e9b1d7b4644 ''Current; in parallel, pages 73, 74, GCSE Combined Science Trilogy; Physics, CGP, AQA '']
 +
:[https://www.amazon.co.uk/gp/product/1782945970/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1782945970&linkCode=as2&tag=nrjc-21&linkId=a120d24dcc7cc7a58192069a3aafc1d2 ''Current; in parallel, pages 75, 76, GCSE Physics; The Complete 9-1 Course for AQA, CGP, AQA '']
 +
:[https://www.amazon.co.uk/gp/product/1782946403/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1782946403&linkCode=as2&tag=nrjc-21&linkId=32a0abb60dff015b15b50e9b1d7b4644 ''Current; in series, page 69, GCSE Combined Science Trilogy; Physics, CGP, AQA '']
 +
:[https://www.amazon.co.uk/gp/product/1782945970/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1782945970&linkCode=as2&tag=nrjc-21&linkId=a120d24dcc7cc7a58192069a3aafc1d2 ''Current; in series, page 71, GCSE Physics; The Complete 9-1 Course for AQA, CGP, AQA '']
 +
:[https://www.amazon.co.uk/gp/product/1782945970/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1782945970&linkCode=as2&tag=nrjc-21&linkId=a120d24dcc7cc7a58192069a3aafc1d2 ''Current; induced, pages 303, 304, GCSE Physics; The Complete 9-1 Course for AQA, CGP, AQA '']
 +
:[https://www.amazon.co.uk/gp/product/1782945970/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1782945970&linkCode=as2&tag=nrjc-21&linkId=a120d24dcc7cc7a58192069a3aafc1d2 ''Current; magnetic field around a current carrying wire, pages 291, 292, GCSE Physics; The Complete 9-1 Course for AQA, CGP, AQA '']
 +
:[https://www.amazon.co.uk/gp/product/1782946403/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1782946403&linkCode=as2&tag=nrjc-21&linkId=32a0abb60dff015b15b50e9b1d7b4644 ''Current; magnetic field around a current-carrying wire, pages 218, 219, GCSE Combined Science Trilogy; Physics, CGP, AQA '']
 +
:[https://www.amazon.co.uk/gp/product/1782946403/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1782946403&linkCode=as2&tag=nrjc-21&linkId=32a0abb60dff015b15b50e9b1d7b4644 ''Current; measuring, pages 235, 236, GCSE Combined Science Trilogy; Physics, CGP, AQA '']
 +
:[https://www.amazon.co.uk/gp/product/1782945970/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1782945970&linkCode=as2&tag=nrjc-21&linkId=a120d24dcc7cc7a58192069a3aafc1d2 ''Current; measuring, pages 331, 332, GCSE Physics; The Complete 9-1 Course for AQA, CGP, AQA '']
 +
:[https://www.amazon.co.uk/gp/product/1471851370/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1471851370&linkCode=as2&tag=nrjc-21&linkId=01c69b0ae058f809cf636033e6ba793e ''Current-potential difference (I-V characteristic) graphs, pages 43-5, GCSE Physics, Hodder, AQA '']
 +
:[https://www.amazon.co.uk/gp/product/1471851354/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1471851354&linkCode=as2&tag=nrjc-21&linkId=9012a0d354024419214fb3ad5ac44ba0 ''Current-potential difference (I-V) graphs, pages 298-9, GCSE Combined Science Trilogy 1, Hodder, AQA '']
 +
:[https://www.amazon.co.uk/gp/product/1471851354/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1471851354&linkCode=as2&tag=nrjc-21&linkId=9012a0d354024419214fb3ad5ac44ba0 ''Current-potential difference (I-V) graphs; investigating the characteristics of a circuit component, page 300, GCSE Combined Science Trilogy 1, Hodder, AQA '']
 +
:[https://www.amazon.co.uk/gp/product/019835939X/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=019835939X&linkCode=as2&tag=nrjc-21&linkId=57e96876985fc39b1a3d8a3e3dc238b6 ''Current-potential difference graphs, page 55, GCSE Physics; Third Edition, Oxford University Press, AQA '']

Latest revision as of 23:21, 3 November 2019

Key Stage 2

Meaning

Electrical Current is the amount of electricity flowing through a wire.

About Electrical Current

The bigger the electrical current the brighter a bulb and the louder a buzzer.
If an electrical current goes through an animal it is called an electrical shock.

Key Stage 3

Meaning

An electrical current is a flow of charge.

About Electrical Current

Current is measured using an Ammeter.
The units of current are amperes, which are also called amps (A).
A current in a wire is a flow of electrons which are negatively charged particles.
Conventional Current flows from positive to negative. This is because electricity was discovered before scientists knew about electrons.
In a salt solution current is the flow of both positive and negative ions.

Key Stage 4

Meaning

Electrical current is the rate of flow of charge.

About Electrical Current

Current is measured using an Ammeter.
The SI Units of current are amperes, which are also called amps (A).
A current in a wire is a flow of electrons which are negatively charged particles.
Conventional Current flows from positive to negative. This is because electricity was discovered before scientists knew about electrons.
In a salt solution current is the flow of both positive and negative ions.
In a series circuit the current is the same everywhere in the circuit.
In a parallel circuit the current splits at a junction.

Equation

Equation Linking Current, Charge and Time

NB: You should remember this equation with charge as the subject of the formula.

Current = (Charge)/(time)

\(I=\frac{Q}{t}\)

Where

\(I\) = The electrical current

\(Q\) = The amount of charge flowing past a point.

\(t\) = The time taken for the charge to flow.

This can give the definition "Current (I) is the (=) amount of charge flowing past a point (Q) per (÷) unit time (t)."

Equation Linking Current, Potential Difference and Resistance

NB: You should remember this equation.

Current = (Potential Difference)/(Resistance)

\(I=\frac{V}{R}\)

Where

\(I\) = The electrical current

\(V\) = The potential difference across a component.

\(R\) = The resistance of an component.

Example Calculations

Finding Current from Charge and Time

A charge of 15 Coulombs passes through a point in a circuit ever 0.52 seconds. Calculate the current flowing past this point correct to two significant figures. A capacitor stores a charge of 10C. It discharges in 12ms. Calculate the current flowing out of the capacitor correct to two significant figures.
1. State the known quantities in correct units.

Q = 15C

t = 0.52s

1. State the known quantities in correct units.

Q = 10C

t = 12ms = 12x10-3s

2. Substitute the numbers into the equation and solve.

\(I=\frac{Q}{t}\)

\(I=\frac{15}{0.52}\)

\(I=28.846153A\)

\(I\approx29A\)

2. Substitute the numbers into the equation and solve.

\(I=\frac{Q}{t}\)

\(I=\frac{10}{12 \times 10^{-3}}\)

\(I=833.3A\)

\(I\approx830A\)

Finding Charge from Current and Time

A battery supplies 4.7Amps to a bulb over a period of 14 seconds. Calculate the charge leaving the battery in this time correct to two significant figures. A hairdryer uses a current of 7.2A for 5 minutes to dry a person’s hair. Calculate the charge flowing through the hairdryer in this time correct to two significant figures.
1. State the known quantities in correct units.

I = 4.7A

t = 14s

1. State the known quantities in correct units.

I = 7.2A

t = 5min = 300s

2. Substitute the numbers and evaluate.

\(I=\frac{Q}{t}\)

\(4.7=\frac{Q}{14}\)

2. Substitute the numbers and evaluate.

\(I=\frac{Q}{t}\)

\(7.2=\frac{Q}{300}\)

3. Rearrange the equation and solve.

\(Q=4.7 \times 14\)

\(Q = 65.8C\)

\(Q \approx 66C\)

3. Rearrange the equation and solve.

\(Q=7.2 \times 300\)

\(Q = 2160C\)

\(Q \approx 2200C\)

Finding Time from Current and Charge

A battery charger uses a current of 150mA to deliver a charge of 245 Coloumbs to a battery. Calculate the time taken to charge this battery correct to two significant figures. A cloud in a thunderstorm loses 15C in one lightening strike. At a current of 31,000kA. Calculate how long this lightning strike lasts correct to two significant figures.
1. State the known quantities in correct units.

I = 150mA = 150x10-3A

Q = 245C

1. State the known quantities in correct units.

I = 31,000kA = 3.1x107A

Q = 15C

2. Substitute the numbers and evaluate.

\(I=\frac{Q}{t}\)

\(150 \times 10^{-3} = \frac{245}{t}\)

2. Substitute the numbers and evaluate.

\(I=\frac{Q}{t}\)

\(3.1 \times 10^7 = \frac{15}{t}\)

3. Rearrange the equation and solve.

\(t=\frac{245}{150 \times 10^{-3}}\)

\(t=1633.3s\)

\(t\approx1633.3s\)

3. Rearrange the equation and solve.

\(t=\frac{15}{3.1 \times 10^7}\)

\(t = 4.8387 \times 10^{-7}s\)

\(t\approx4.8 \times 10^{-7}s\)

Finding Current from Potential Difference and Resistance

A potential difference of 9.9V is placed across an 19 Ohm resistor. Calculate the current flowing through the resistor correct to two significant figures. A toaster has a resistance of 27 Ohms is plugged into the mains which has a potential difference of 230V. Calculate the current flowing through the toaster correct to two significant figures.
1. State the known quantities in correct units.

V = 9.9V

R = 19Ω

1. State the known quantities in correct units.

V = 230V

R = 27Ω

2. Substitute the numbers into the equation and solve.

\(I=\frac{V}{R}\)

\(I=\frac{9.9}{19}\)

\(I=0.52105A\)

\(I\approx0.52A\)

2. Substitute the numbers into the equation and solve.

\(I=\frac{V}{R}\)

\(I=\frac{230}{27}\)

\(I=8.519A\)

\(I\approx8.5A\)

Finding Resistance from Potential Difference and Current

A student measures a potential difference of 5.4V and a current of 0.13mA across a component. Calculate the resistance of the component. Calculating the resistance of a buzzer connected in series to a 9V battery with an ammeter reading of 23mA.
1. State the known quantities in correct units.

V = 5.4V

I = 0.13mA = 0.13x10-3

1. State the known quantities in correct units.

V = 9V

I = 23mA = 23x10-3

2. Substitute the numbers and evaluate.

\(I=\frac{V}{R}\)

\(0.13 \times 10^{-3}=\frac{5.4}{R}\)

2. Substitute the numbers and evaluate.

\(23 \times 10^{-3}=\frac{9}{R}\)

3. Rearrange the equation and solve.

\(R=\frac{5.4}{0.13 \times 10^{-3}}\)

\(R=41538.46\Omega\)

\(R\approx 42000\Omega\)

3. Rearrange the equation and solve.

\(R=\frac{9}{23 \times 10^{-3}}\)

\(R=391.3043\Omega\)

\(R\approx 390\Omega\)

Finding Potential Difference from Current and Resistance

A current of 55mA flows through a component with a resistance of 93 Ohms. Calculate the potential difference across this component correct to two significant figures. A 22kΩ resistor has a current flowing through it of 6mA. Calculate the potential difference across the resistor correct to two significant figures.
1. State the known quantities in correct units.

I = 55mA = 55x10-3A

R = 93Ω

1. State the known quantities in correct units.

I = 6mA = 6x10-3A

R = 22kΩ = 22x103Ω

2. Substitute the numbers and evaluate.

\(I=\frac{V}{R}\)

\(55 \times 10^{-3}=\frac{V}{93}\)

2. Substitute the numbers and evaluate.

\(I=\frac{V}{R}\)

\(6 \times 10^{-3}=\frac{V}{22 \times 10^3}\)

3. Rearrange the equation and solve.

\(V= 55 \times 10^{-3} \times 93\)

\(V= 5.115V\)

\(V\approx5.1V\)

3. Rearrange the equation and solve.

\(V= 6 \times 10^{-3} \times 22 \times 10^3\)

\(V= 132V\)

\(V\approx130V\)


References

AQA

Current (electrical), pages 180, 181, 190, GCSE Combined Science; The Revision Guide, CGP, AQA
Current (electrical), pages 24, 33, GCSE Physics; The Revision Guide, CGP, AQA
Current (electrical); alternating, page 188, GCSE Combined Science; The Revision Guide, CGP, AQA
Current (electrical); alternating, pages 31, 96, 97, GCSE Physics; The Revision Guide, CGP, AQA
Current (electrical); direct, page 188, GCSE Combined Science; The Revision Guide, CGP, AQA
Current (electrical); direct, pages 31, 97, GCSE Physics; The Revision Guide, CGP, AQA
Current (electrical); energy transferred, page 190, GCSE Combined Science; The Revision Guide, CGP, AQA
Current (electrical); I-V characteristics, page 183, GCSE Combined Science; The Revision Guide, CGP, AQA
Current (electrical); I-V characteristics, page 26, GCSE Physics; The Revision Guide, CGP, AQA
Current (electrical); magnetic field around a current-carrying wire, page 230, GCSE Combined Science; The Revision Guide, CGP, AQA
Current (electrical); magnetic field around a current-carrying wire, pages 93, 94, GCSE Physics; The Revision Guide, CGP, AQA
Current (electrical); mains supply, page 188, GCSE Combined Science; The Revision Guide, CGP, AQA
Current (electrical); national grid, page 191, GCSE Combined Science; The Revision Guide, CGP, AQA
Current (electrical); parallel circuits, pages 186-187, GCSE Combined Science; The Revision Guide, CGP, AQA
Current (electrical); series circuits, pages 185-187, GCSE Combined Science; The Revision Guide, CGP, AQA
Current, pages 46-7, 52-69, 72-5, 247-9, GCSE Physics; Student Book, Collins, AQA
Current, pages 52-53, 58-61, 64-65, 68-71, 216-229, GCSE Physics; Third Edition, Oxford University Press, AQA
Current, pages 61-67, GCSE Combined Science Trilogy; Physics, CGP, AQA
Current, pages 63-69, GCSE Physics; The Complete 9-1 Course for AQA, CGP, AQA
Current; alternating (ac), pages 86, 203, GCSE Combined Science Trilogy; Physics, CGP, AQA
Current; alternating (ac), pages 89, 245, 306, GCSE Physics; The Complete 9-1 Course for AQA, CGP, AQA
Current; direct (dc), page 86, GCSE Combined Science Trilogy; Physics, CGP, AQA
Current; direct (dc), pages 89, 306, GCSE Physics; The Complete 9-1 Course for AQA, CGP, AQA
Current; in parallel, pages 73, 74, GCSE Combined Science Trilogy; Physics, CGP, AQA
Current; in parallel, pages 75, 76, GCSE Physics; The Complete 9-1 Course for AQA, CGP, AQA
Current; in series, page 69, GCSE Combined Science Trilogy; Physics, CGP, AQA
Current; in series, page 71, GCSE Physics; The Complete 9-1 Course for AQA, CGP, AQA
Current; induced, pages 303, 304, GCSE Physics; The Complete 9-1 Course for AQA, CGP, AQA
Current; magnetic field around a current carrying wire, pages 291, 292, GCSE Physics; The Complete 9-1 Course for AQA, CGP, AQA
Current; magnetic field around a current-carrying wire, pages 218, 219, GCSE Combined Science Trilogy; Physics, CGP, AQA
Current; measuring, pages 235, 236, GCSE Combined Science Trilogy; Physics, CGP, AQA
Current; measuring, pages 331, 332, GCSE Physics; The Complete 9-1 Course for AQA, CGP, AQA
Current-potential difference (I-V characteristic) graphs, pages 43-5, GCSE Physics, Hodder, AQA
Current-potential difference (I-V) graphs, pages 298-9, GCSE Combined Science Trilogy 1, Hodder, AQA
Current-potential difference (I-V) graphs; investigating the characteristics of a circuit component, page 300, GCSE Combined Science Trilogy 1, Hodder, AQA
Current-potential difference graphs, page 55, GCSE Physics; Third Edition, Oxford University Press, AQA
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