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===About Resistance===
: The [[SI Unit|unit]] of '''resistance''' is the [[Ohm]] ([[Ω]]).
: '''Resistance''' cannot be directly [[measure]]d. '''Resistance''' must be calculated by dividing the [[Potential Difference]] by the [[Electrical Current|Current]].
: [[Electrical Conductor|Conductors]] have a low '''resistance''' and [[Electrical Insulator|insulator]]s have a high '''resistance'''.
===Equation===
:<math>R = \frac{V}{I}</math>
Where:
: <math>R </math> = '''Resistance''' of a [[Electrical Component|component]].: <math>V </math> = The [[Potential Difference]] across the [[Electrical Component|component]].: <math>I </math> = The [[Electrical Current|current]] through the [[Electrical Component|component]].
===Example Calculations===
{| class="wikitable"
|-
| style="height:20px; width:200px; text-align:center;" |'''A student [[measure]]s a [[Potential Difference|potential difference]] of 5[[V]] 5V across a [[component]] and a [[Electrical Current|current]] of 0.1[[A]]1A. Calculate the resistance.'''| style="height:20px; width:200px; text-align:center;" |'''A [[Electrical Bulb|bulb]] has a [[Electrical Current|current]] of 200[[mA]] 200mA passing through it and a [[Potential Difference|potential difference]] of 12[[V]] 12V across it. Calculate the resistance of the [[Electrical Bulb|bulb]].'''| style="height:20px; width:200px; text-align:center;" |'''Calculate the resistance of a [[buzzer]] connected in [[Series Circuit|series]] to a 6[[V]] 6V [[battery]] with an [[ammeter]] reading of 10[[mA]]10mA.'''
|-
| style="height:20px; width:200px; text-align:left;" |
Potential Difference = 5[[V]]5V
Current = 0.1[[A]]1A
<math>R = \frac{V}{I}</math>
<math> R = 50 \Omega</math>
| style="height:20px; width:200px; text-align:left;" |
Potential Difference = 12[[V]]12V
Current = 200[[mA]] = 0.2[[A]]2A
<math>R = \frac{V}{I}</math>
<math> R = 60 \Omega</math>
| style="height:20px; width:200px; text-align:left;" |
Potential Difference = 6[[V]]6V
Current = 10[[mA]] 10mA = 0.01[[A]]01A
<math>R = \frac{V}{I}</math>
<math> R = 600 \Omega</math>
|}
==Key Stage 4==
===Meaning===
'''Resistance''' is the [[ratio]] of [[Potential Difference|potential difference]] to [[Electrical Current|current]].
===About Resistance===
: The [[SI Unit|unit]] of '''resistance''' is the [[Ohm]] ([[Ω]]).
: '''Resistance''' cannot be directly [[measure]]d. '''Resistance''' must be calculated by dividing the [[Potential Difference]] by the [[Electrical Current|Current]].
: [[Electrical Conductor|Conductors]] have a low '''resistance''' and [[Electrical Insulator|insulator]]s have a high '''resistance'''.
===Equation===
'''Resistance''' = (Potential Difference)/(Current)
:<math>R = \frac{V}{I}</math>
Where:
: <math>R</math> = '''Resistance''' of a [[Electrical Component|component]].
: <math>V</math> = The [[Potential Difference]] across the [[Electrical Component|component]].
: <math>I</math> = The [[Electrical Current|current]] through the [[Electrical Component|component]].
===Example Calculations===
{| class="wikitable"
|-
| style="height:20px; width:300px; text-align:center;" |'''A student [[measure]]s a [[Potential Difference|potential difference]] of 5.9[[V]] across a [[component]] and a [[Electrical Current|current]] of 0.11[[A]]. Calculate the resistance correct to two [[Significant Figures|significant figures]].'''
| style="height:20px; width:300px; text-align:center;" |'''Calculate the resistance of a [[buzzer]] connected in [[Series Circuit|series]] to a 9V [[battery]] with an [[ammeter]] reading of 23mA correct to two [[Significant Figures|significant figures]].'''
|-
| style="height:20px; width:200px; text-align:left;" |'''1. State the known quantities in correct [[unit]]s.'''
Potential Difference = 5.9V
Current = 0.11A
| style="height:20px; width:200px; text-align:left;" |'''1. State the known quantities in correct [[unit]]s.'''
Potential Difference = 9V
Current = 23mA = 23x10<sup>-3</sup>A
| style="height:20px; width:200px; text-align:left;" |'''2. [[Substitute (Maths)|Substitute]] the numbers into the [[equation]] and [[Solve (Maths)|solve]].'''
<math>R = \frac{V}{I}</math>
<math>R = \frac{5.9}{0.11}</math>
<math> R = 53.635 \Omega</math>
<math> R \approx 54\Omega</math>
| style="height:20px; width:200px; text-align:left;" |'''2. [[Substitute (Maths)|Substitute]] the numbers into the [[equation]] and [[Solve (Maths)|solve]].'''
<math>R = \frac{V}{I}</math>
<math>R = \frac{9}{23\times10^{-3}}</math>
<math> R = 391.304 \Omega</math>
<math> R \approx 390 \Omega</math>
|}