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{| class="wikitable"
 
{| class="wikitable"
 
|[[File:PhetCharges.png|centre|300px|link=https://phet.colorado.edu/sims/html/charges-and-fields/latest/charges-and-fields_en.html]]
 
|[[File:PhetCharges.png|centre|300px|link=https://phet.colorado.edu/sims/html/charges-and-fields/latest/charges-and-fields_en.html]]
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|}
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==Key Stage 4==
 +
===Meaning===
 +
'''Charge''' is a [[property]] of [[matter]] that can cause an [[Electrostatic Force|electrostatic force]] between two [[object]]s.
 +
 +
===About Charge===
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: There are two types of '''charge'''; [[Positive Charge|positive]] and [[Negative Charge|negative]].
 +
: Like '''charges''' [[repel]] each other and opposite '''charges''' [[attract]] each other.
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: '''Charges''' create an [[Electrostatic Field|electrostatic field]] which affects other '''charged''' [[object]]s.
 +
: '''Charge''' is a conserved quantity which means; "'''Charge''' cannot be created or destroyed, it can only be transferred from one place to another."
 +
: A flow of '''charge''' is an [[Electrical Current|electrical current]].
 +
 +
===Equation===
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====Equation linking Charge, Current and Time====
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''NB: You should remember this equation with charge as the subject of the formula.''
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'''Charge''' = (Current) x (time)
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<math>Q=It</math>
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Where:
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<math>Q</math> = The amount of [[Electrical Charge|charge]] flowing past a point.
 +
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<math>I</math> = The '''electrical current'''
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<math>t</math> = The [[time]] taken for the [[Electrical Charge|charge]] to flow.
 +
 +
====Equation linking Charge, Potential Difference and Energy Transferred====
 +
''NB: You should remember this equation with energy transferred as the subject of the formula.''
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'''Charge''' = (Energy Transferred)/(Potential Difference)
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<math>Q=\frac{E}{V}</math>
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 +
Where:
 +
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<math>Q</math> = The amount of [[Electrical Charge|charge]].
 +
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<math>E</math> = The [[Energy Transfer]]red by the '''charge'''.
 +
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<math>V</math> = The [[Potential Difference|potential difference]] between two points.
 +
 +
===Example Calculations===
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====Finding Current from Charge and Time====
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{| class="wikitable"
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| 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:left;" |'''1. State the known quantities in correct [[unit]]s.'''
 +
 +
Q = 15C
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 +
t = 0.52s
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| style="height:20px; width:300px; text-align:left;" |'''1. State the known quantities in correct [[unit]]s.'''
 +
 +
Q = 10C
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t = 12ms = 12x10<sup>-3</sup>s
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|-
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| style="height:20px; width: 300px; text-align:left;" |'''2. [[Substitute (Maths)|Substitute]] the numbers and [[Evaluate (Maths)|evaluate]].'''
 +
 +
<math>Q=It</math>
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<math>15=I \times 0.52</math>
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| style="height:20px; width: 300px; text-align:left;" |'''2. [[Substitute (Maths)|Substitute]] the numbers and [[Evaluate (Maths)|evaluate]].'''
 +
 +
<math>Q=It</math>
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<math>10=I \times 12 \times 10^{-3}</math>
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| style="height:20px; width: 300px; text-align:left;" |'''3. [[Rearrange (Maths)|Rearrange]] the equation and [[Solve (Maths)|solve]].'''
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<math>I=\frac{15}{0.52}</math>
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<math>I=28.846153A</math>
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<math>I\approx29A</math>
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| style="height:20px; width: 300px; text-align:left;" |'''3. [[Rearrange (Maths)|Rearrange]] the equation and [[Solve (Maths)|solve]].'''
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<math>I=\frac{10}{12 \times 10^{-3}}</math>
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<math>I=833.3A</math>
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<math>I\approx830A</math>
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|}
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====Finding Charge from Current and Time====
 +
{| class="wikitable"
 +
| 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 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]].
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|-
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| style="height:20px; width: 300px; text-align:left;" |'''1. State the known quantities in correct [[unit]]s.'''
 +
 +
I = 4.7A
 +
 +
t = 14s
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| style="height:20px; width: 300px; text-align:left;" |'''1. State the known quantities in correct [[unit]]s.'''
 +
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I = 7.2A
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t = 5min = 300s
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|-
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| style="height:20px; width:200px; text-align:left;" |'''2. [[Substitute (Maths)|Substitute]] the numbers into the [[equation]] and [[Solve (Maths)|solve]].'''
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<math>Q=It</math>
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<math>Q=4.7 \times 14</math>
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<math>Q = 65.8C</math>
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<math>Q \approx 66C</math>
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| style="height:20px; width:200px; text-align:left;" |'''2. [[Substitute (Maths)|Substitute]] the numbers into the [[equation]] and [[Solve (Maths)|solve]].'''
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<math>Q=It</math>
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<math>Q=7.2 \times 300</math>
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<math>Q = 2160C</math>
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<math>Q \approx 2200C</math>
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|}
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====Finding Time from Current and Charge====
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{| class="wikitable"
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| 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]].
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| style="height:20px; width: 300px; text-align:center;" |A cloud in a thunderstorm loses 15kC in one lightening strike. At a current of 31,000kA. Calculate how long this lightning strike lasts correct to two [[Significant Figures|significant figures]].
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|-
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| style="height:20px; width: 300px; text-align:left;" |'''1. State the known quantities in correct [[unit]]s.'''
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I = 150mA = 150x10<sup>-3</sup>A
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Q = 245C
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| style="height:20px; width: 300px; text-align:left;" |'''1. State the known quantities in correct [[unit]]s.'''
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I = 31,000kA = 3.1x10<sup>7</sup>A
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Q = 15kC = 15x10<sup>3</sup>
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|-
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| style="height:20px; width: 300px; text-align:left;" |'''2. [[Substitute (Maths)|Substitute]] the numbers and [[Evaluate (Maths)|evaluate]].'''
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<math>Q=It</math>
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<math>245 = 150 \times 10^{-3} \times t</math>
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| style="height:20px; width: 300px; text-align:left;" |'''2. [[Substitute (Maths)|Substitute]] the numbers and [[Evaluate (Maths)|evaluate]].'''
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<math>Q=It</math>
 +
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<math>15 \times 10^3 = 3.1 \times 10^7 \times t</math>
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|-
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| style="height:20px; width: 300px; text-align:left;" |'''3. [[Rearrange (Maths)|Rearrange]] the equation and [[Solve (Maths)|solve]].'''
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<math>t=\frac{245}{150 \times 10^{-3}}</math>
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<math>t=1633.3s</math>
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<math>t\approx1633.3s</math>
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| style="height:20px; width: 300px; text-align:left;" |'''3. [[Rearrange (Maths)|Rearrange]] the equation and [[Solve (Maths)|solve]].'''
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<math>t=\frac{15 \times 10^3}{3.1 \times 10^7}</math>
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<math>t = 4.8387 \times 10^{-4}s</math>
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<math>t\approx4.8 \times 10^{-4}s</math>
 
|}
 
|}

Revision as of 09:48, 25 February 2019

Key Stage 3

Meaning

Charge is a property of matter that can cause an electrostatic force between two objects.

About Charge

There are two types of charge; positive and negative.
Like charges repel each other and opposite charges attract each other.
Charges create an electrostatic field which affects other charged objects.

To see the electrostatic field created by a charge click on the picture below to play a PHET simulation.

PhetCharges.png

Key Stage 4

Meaning

Charge is a property of matter that can cause an electrostatic force between two objects.

About Charge

There are two types of charge; positive and negative.
Like charges repel each other and opposite charges attract each other.
Charges create an electrostatic field which affects other charged objects.
Charge is a conserved quantity which means; "Charge cannot be created or destroyed, it can only be transferred from one place to another."
A flow of charge is an electrical current.

Equation

Equation linking Charge, Current and Time

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

Charge = (Current) x (time)

\(Q=It\)

Where\[Q\] = The amount of charge flowing past a point.

\(I\) = The electrical current

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

Equation linking Charge, Potential Difference and Energy Transferred

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

Charge = (Energy Transferred)/(Potential Difference)

\(Q=\frac{E}{V}\)

Where\[Q\] = The amount of charge.

\(E\) = The Energy Transferred by the charge.

\(V\) = The potential difference between two points.

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 and evaluate.

\(Q=It\)

\(15=I \times 0.52\)

2. Substitute the numbers and evaluate.

\(Q=It\)

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

3. Rearrange the equation and solve.

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

\(I=28.846153A\)

\(I\approx29A\)

3. Rearrange the equation and solve.

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

\(I=833.3A\)

\(I\approx830A\)

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 into the equation and solve.

\(Q=It\)

\(Q=4.7 \times 14\)

\(Q = 65.8C\)

\(Q \approx 66C\)

2. Substitute the numbers into the equation and solve.

\(Q=It\)

\(Q=7.2 \times 300\)

\(Q = 2160C\)

\(Q \approx 2200C\)

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 15kC 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 = 15kC = 15x103

2. Substitute the numbers and evaluate.

\(Q=It\)

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

2. Substitute the numbers and evaluate.

\(Q=It\)

\(15 \times 10^3 = 3.1 \times 10^7 \times t\)

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.

\(t=\frac{15 \times 10^3}{3.1 \times 10^7}\)

\(t = 4.8387 \times 10^{-4}s\)

\(t\approx4.8 \times 10^{-4}s\)

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