A ==Key Stage 3=====Meaning==='''Resistance''' is a description of how difficult it is to increase the [[Electrical Current|current]] through a [[Electrical Conductor|conductor]] when increasing the [[Potential Difference|potential difference]]. ===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:200px; text-align:center;" |'''A student [[measure]]s a [[Potential Difference|potential difference]] of 5V across a [[increasecomponent]] and a [[Electrical Current|current]] of 0.1A. Calculate the resistance.'''| style="height:20px; width:200px; text-align:center;" |'''A [[Electrical Bulb|bulb]] has a [[Electrical Current|current]] of 200mA passing through it and a [[Potential Difference|potential difference]] of 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 6V [[battery]] with an [[ammeter]] reading of 10mA.'''|-| style="height:20px; width:200px; text-align:left;" |Potential Difference = 5V Current = 0.1A <math>R = \frac{V}{I}</math> <math>R = \frac{5}{0.1}</math> <math> R = 50 \Omega</math>| style="height:20px; width:200px; text-align:left;" |Potential Difference = 12V Current = 200mA = 0.2A <math>R = \frac{V}{I}</math> <math>R = \frac{12}{0.2}</math> <math> R = 60 \Omega</math>| style="height:20px; width:200px; text-align:left;" |Potential Difference = 6V Current = 10mA = 0.01A <math>R = \frac{V}{I}</math> <math>R = \frac{6}{0.01}</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'''.: '''Resistance''' in a [[wire]] is caused by [[electron]]s colliding with [[Positive Ion|positive ion]]s in the [[metal]] [[lattice]].{| class="wikitable"|-|[[File:ResistanceCause.png|center|500px]]|-| style="height:20px; width:200px; text-align:center;" |This [[diagram]] shows [[electron]]s moving past the [[Positive Ion|positive ions]] in a [[metal]] [[lattice]]. As they move some of them collide with the [[Positive Ion|positive ions]] in the [[lattice]] which is acts as a '''resistance''' to an [[Electrical Current|electrical current]].|}: The higher the [[temperature]] of a [[Electrical Conductor|conductor]] when changing the greater the '''resistance''' of that [[Electrical Conductor|conductor]]. This is due to the [[metal]] [[ion]]s vibrating faster at higher [[temperature]]s which makes [[electron]]s more likely to collide with the [[ion]]s as they pass through the [[Electrical Conductor|conductor]]. ===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=======Finding Resistance from Current and Potential Difference===={| class="wikitable"|-| style="height:20px; width:300px; text-align:center;" |'''A student [[measure]]s a [[Potential Difference|potential difference]] of 5.9V across a [[component]] and a [[Electrical Current|current]] of 0.11A. 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>|} ====Finding Current from Potential Difference and Resistance===={| class="wikitable"| 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:left;" |'''1. State the known quantities in correct [[unit]]s.''' V = 9.9V R = 19Ω| style="height:20px; width:300px; text-align:left;" |'''1. State the known quantities in correct [[unit]]s.'''V = 230V R = 27Ω|-| style="height:20px; width: 300px; text-align:left;" |'''2. [[Substitute (Maths)|Substitute]] the numbers and [[Evaluate (Maths)|evaluate]].''' <math>R = \frac{V}{I}</math> <math>19=\frac{9.9}{I}</math> | style="height:20px; width: 300px; text-align:left;" |'''2. [[Substitute (Maths)|Substitute]] the numbers and [[Evaluate (Maths)|evaluate]].''' <math>R = \frac{V}{I}</math> <math>27=\frac{230}{R}</math>|-| style="height:20px; width: 300px; text-align:left;" |'''3. [[Rearrange (Maths)|Rearrange]] the equation and [[Solve (Maths)|solve]].''' <math>I=\frac{9.9}{19}</math> <math>I=0.52105A</math> <math>I\approx0.52A</math> | style="height:20px; width: 300px; text-align:left;" |'''3. [[Rearrange (Maths)|Rearrange]] the equation and [[Solve (Maths)|solve]].''' <math>I=\frac{230}{27}</math> <math>I=8.519A</math> <math>I\approx8.5A</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>R = \frac{V}{I}</math> <math>93=\frac{V}{55 \times 10^{-3}}</math>| style="height:20px; width: 300px; text-align:left;" |'''2. [[Substitute (Maths)|Substitute]] the numbers and [[Evaluate (Maths)|evaluate]].''' <math>R = \frac{V}{I}</math> <math>22 \times 10^3=\frac{V}{6 \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/1782946403/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1782946403&linkCode=as2&tag=nrjc-21&linkId=32a0abb60dff015b15b50e9b1d7b4644 ''Resistance (electrical), page 63, 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 ''Resistance (electrical), page 65, GCSE Physics; The Complete 9-1 Course for AQA, 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=ad276ad49df77ab4b40ab4fd0fe10246 ''Resistance (electrical), pages 180-184, 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=f0dfb66dafcb0c6e9449e7b1a4ae1ac384 ''Resistance (electrical), pages 24-30, 32, 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=ad276ad49df77ab4b40ab4fd0fe10247 ''Resistance (electrical); in parallel circuits, pages 186, 187, 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=f0dfb66dafcb0c6e9449e7b1a4ae1ac385 ''Resistance (electrical); in parallel circuits, pages 29, 30, GCSE Physics; The Revision Guide, 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 ''Resistance (electrical); in parallel, pages 74, 77-79, 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 ''Resistance (electrical); in parallel, pages 76, 79-81, GCSE Physics; The Complete 9-1 Course for AQA, 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=ad276ad49df77ab4b40ab4fd0fe10248 ''Resistance (electrical); in series circuits, pages 185, 187, 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=f0dfb66dafcb0c6e9449e7b1a4ae1ac386 ''Resistance (electrical); in series circuits, pages 28, 30, GCSE Physics; The Revision Guide, 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 ''Resistance (electrical); in series, pages 70, 77, 78, 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 ''Resistance (electrical); in series, pages 72, 79, 80, 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 ''Resistance (electrical); investigating, pages 64, 77-79, 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 ''Resistance (electrical); investigating, pages 66, 79-81, 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 ''Resistance (electrical); of diodes, page 66, 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 ''Resistance (electrical); of diodes, page 68, 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 ''Resistance (electrical); of filament lamps, page 66, 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 ''Resistance (electrical); of filament lamps, page 68, 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 ''Resistance (electrical); of LDRs, page 80, 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 ''Resistance (electrical); of LDRs, page 82, 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 ''Resistance (electrical); of resistors, pages 65, 66, 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 ''Resistance (electrical); of resistors, pages 67, 68, 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 ''Resistance (electrical); of thermistors, pages 80, 81, 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 ''Resistance (electrical); of thermistors, pages 82, 83, GCSE Physics; The Complete 9-1 Course for AQA, 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=ad276ad49df77ab4b40ab4fd0fe10249 ''Resistance (electrical); wire length, page 182, GCSE Combined Science; The Revision Guide, CGP, AQA '']