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→Key Stage 3
: The [[SI Unit|units]] of '''potential difference''' are [[Volt]]s ([[V]]).
: '''Potential Difference''' is sometimes described as the 'push' that moves a [[Electrical Current|current]] around a [[circuit]].
==Key Stage 4==
===Meaning===
[[Potential Difference]] is the amount of [[energy]] is [[Energy Transfer|transferred]] per unit [[Electrical Charge|charge]] between two points in a [[Electrical Circuit|circuit]].
===About Potential Difference===
: '''Potential Difference''' is [[measure]]d using a [[Voltmeter]].
: The [[SI Unit|units]] of '''potential difference''' are [[Volt]]s ([[V]]).
: '''Potential difference''' is the difference in '''potential''' between two points in a [[Electrical Circuit|circuit]].
: '''Potential difference''' can be [[measure]]d between two points in a [[Electrical Circuit|circuit]] and is [[measure]]d across a [[Electrical Component|component]].
: If two points in a [[Electrical Circuit|circuit]] are at the same '''potential''' there is no '''potential difference''' between them so no [[energy]] is [[Energy Transfer|transferred]] between those two points.
===Equation===
''NB: You should remember this equation with energy transferred as the subject of the formula.''
'''Charge''' = (Energy Transferred)/(Potential Difference)
<math>V=\frac{E}{Q}</math>
Where:
<math>V</math> = The [[Potential Difference|potential difference]] between two points.
<math>Q</math> = The amount of [[Electrical Charge|charge]] that move between two points.
<math>E</math> = The [[Energy Transfer]]red by the '''charge'''.
===Example Calculations===
====Finding Charge from Potential Difference and Energy Transferred====
{| class="wikitable"
| style="height:20px; width:300px; text-align:center;" |The [[Potential Difference|potential difference]] of 12V is placed across a [[Electrical Resistor|resistor]] increasing its [[Thermal Energy Store|thermal energy store]] by 3.7J as a result. Calculate the '''charge''' that has flowed through the [[Electrical Resistor|resistor]] in this time correct to two [[Significant Figures|significant figures]].
| style="height:20px; width:300px; text-align:center;" |A [[circuit]] transfers 2.8kJ of [[energy]] [[electrically]] to a [[motor]]. The [[Potential Difference|potential difference]] across the [[motor]] is 1.5V. Calculate the'''charge''' that has flowed through the [[motor]] in this time correct to two [[Significant Figures|significant figures]].
|-
| style="height:20px; width:300px; text-align:left;" |'''1. State the known quantities in correct [[unit]]s.'''
V = 12V
E = 3.7J
| style="height:20px; width:300px; text-align:left;" |'''1. State the known quantities in correct [[unit]]s.'''
V = 1.5V
E = 2.8kJ = 2.8x10<sup>3</sup>J
|-
| style="height:20px; width: 300px; text-align:left;" |'''2. [[Substitute (Maths)|Substitute]] the numbers and [[Evaluate (Maths)|evaluate]].'''
<math>V=\frac{E}{Q}</math>
<math>12=\frac{3.7}{Q}</math>
| style="height:20px; width: 300px; text-align:left;" |'''2. [[Substitute (Maths)|Substitute]] the numbers and [[Evaluate (Maths)|evaluate]].'''
<math>V=\frac{E}{Q}</math>
<math>1.5=\frac{2.8 \times 10^3}{Q}</math>
|-
| style="height:20px; width: 300px; text-align:left;" |'''3. [[Rearrange (Maths)|Rearrange]] the equation and [[Solve (Maths)|solve]].'''
<math>Q=\frac{3.7}{12}</math>
<math>Q=0.3083C</math>
<math>Q\approx0.31C</math>
| style="height:20px; width: 300px; text-align:left;" |'''3. [[Rearrange (Maths)|Rearrange]] the equation and [[Solve (Maths)|solve]].'''
<math>Q=\frac{2.8 \times 10^3}{1.5}</math>
<math>Q=1866.7C</math>
<math>Q\approx1900C</math>
|}
====Finding Potential Difference from Charge and Energy Transferred====
{| class="wikitable"
| style="height:20px; width: 300px; text-align:center;" |A '''charge''' of 84C transfers an [[energy]] of 20kJ. Calculate the [[Potential Difference|potential difference]] correct to two [[Significant Figures|significant figures]].
| style="height:20px; width: 300px; text-align:center;" |170J of [[energy]] is transferred by a '''charge''' of 92mC. Calculate the [[Potential Difference|potential difference]] 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 = 84C
E = 20kJ = 20x10<sup>3</sup>J
| style="height:20px; width: 300px; text-align:left;" |'''1. State the known quantities in correct [[unit]]s.'''
Q = 92mC = 92x10<sup>-3<sup>C
E = 170J
|-
| style="height:20px; width:200px; text-align:left;" |'''2. [[Substitute (Maths)|Substitute]] the numbers into the [[equation]] and [[Solve (Maths)|solve]].'''
<math>V=\frac{E}{Q}</math>
<math>V=\frac{20 \times 10^3}{84}</math>
<math>V=238.0952V</math>
<math>V\approx 240V</math>
| style="height:20px; width:200px; text-align:left;" |'''2. [[Substitute (Maths)|Substitute]] the numbers into the [[equation]] and [[Solve (Maths)|solve]].'''
<math>V=\frac{E}{Q}</math>
<math>V=\frac{170}{92 \times 10^{-3}}</math>
<math>V=1847.826V</math>
<math>V\approx = 1800V</math>
|}
====Finding Energy Transferred from Charge and Potential Difference====
{| class="wikitable"
| style="height:20px; width: 300px; text-align:center;" |A bolt of lightning with a [[Potential Difference|potential difference]] 31,000kV transfers a '''charge''' of 15C. Calculate the [[Energy Transfer|energy transferred]] by this bolt of [[lightning]] correct to two [[Significant Figures|significant figures]].
| style="height:20px; width: 300px; text-align:center;" |A 9V [[Electrical Battery|battery]] is able to mobilise a '''charge''' of 4.3kC during its operation. Calculate the total amount of [[energy]] stored in this [[Electrical Battery|battery]] correct to two [[Significant Figures|significant figures]].
|-
| style="height:20px; width: 300px; text-align:left;" |'''1. State the known quantities in correct [[unit]]s.'''
V = 31,000kV = 3.1x10<sup>7<sup>V
Q = 15C
| style="height:20px; width: 300px; text-align:left;" |'''1. State the known quantities in correct [[unit]]s.'''
V = 9V
Q = 4.3kC = 4.3x10<sup>3</sup>
|-
| style="height:20px; width: 300px; text-align:left;" |'''2. [[Substitute (Maths)|Substitute]] the numbers and [[Evaluate (Maths)|evaluate]].'''
<math>V=\frac{E}{Q}</math>
<math>3.1 \times 10^7=\frac{E}{15}</math>
| style="height:20px; width: 300px; text-align:left;" |'''2. [[Substitute (Maths)|Substitute]] the numbers and [[Evaluate (Maths)|evaluate]].'''
<math>V=\frac{E}{Q}</math>
<math>9 =\frac{E}{4.3 \times 10^3}</math>
|-
| style="height:20px; width: 300px; text-align:left;" |'''3. [[Rearrange (Maths)|Rearrange]] the equation and [[Solve (Maths)|solve]].'''
<math>E = 15 \times 3.1 \times 10^7</math>
<math>E = 4.65\times10^8 J</math>
<math>E\approx4.7\times10^8 J</math>
| style="height:20px; width: 300px; text-align:left;" |'''3. [[Rearrange (Maths)|Rearrange]] the equation and [[Solve (Maths)|solve]].'''
<math>E = 4.3 \times 10^3 \times 9</math>
<math>E = 38700J</math>
<math>E \approx 39000 \times 10^4J</math>
|}