Difference between revisions of "Electrical Resistance"
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: V = Potential Difference | : V = Potential Difference | ||
: I = Current | : I = Current | ||
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===Example Calculations=== | ===Example Calculations=== | ||
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| style="height:20px; width:200px; text-align:left;" | | | style="height:20px; width:200px; text-align:left;" | | ||
| − | + | Potential Difference = 5[[V]] | |
| − | + | Current = 0.1[[A]] | |
| − | <math> | + | :<math>R = \tfrac{V}{I}</math> |
| − | <math> | + | :<math>R = \tfrac{5}{0.1}</math> |
| − | <math> | + | <math> R = 50\ohm</math> |
| style="height:20px; width:200px; text-align:left;" | | | style="height:20px; width:200px; text-align:left;" | | ||
Force = 10,000N | Force = 10,000N | ||
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Distance moved in the direction of the force = 15m | Distance moved in the direction of the force = 15m | ||
| − | <math> | + | :<math>R = \tfrac{V}{I}</math> |
<math> W = 10,000 \times 15</math> | <math> W = 10,000 \times 15</math> | ||
| Line 54: | Line 48: | ||
Distance moved in the direction of the force = 0m | Distance moved in the direction of the force = 0m | ||
| − | <math> | + | :<math>R = \tfrac{V}{I}</math> |
<math> W = 20 \times 0</math> | <math> W = 20 \times 0</math> | ||
Revision as of 08:50, 26 October 2018
Key Stage 3
Meaning
Resistance is a description of how difficult it is to increase the current through a conductor when increasing the potential difference.
About Resistance
- The unit of resistance is the Ohm (Ω).
- Resistance cannot be directly measured. Resistance must be calculated by dividing the Potential Difference by the Current.
- Conductors have a low resistance and insulators have a high resistance.
Equation
\[Resistance = \tfrac{Potential Difference}{Current}\] \[R = \tfrac{V}{I}\] Where:
- R = Resistance
- V = Potential Difference
- I = Current
Example Calculations
| A student measures a potential difference of 5V across a component and a current of 0.1A. Calculate the resistance. | A bulb has a current of 200mA passing through it and a potential difference of 12V across it. Calculate the resistance of the bulb. | Calculate the resistance of a buzzer connected in series to a 6V battery with an ammeter reading of 10mA. |
|
Potential Difference = 5V Current = 0.1A \[R = \tfrac{V}{I}\] \[R = \tfrac{5}{0.1}\] \( R = 50\ohm\) |
Force = 10,000N Distance moved in the direction of the force = 15m \[R = \tfrac{V}{I}\] \( W = 10,000 \times 15\) \( W = 15,000J\) |
Force = 40N Distance moved in the direction of the force = 0m \[R = \tfrac{V}{I}\] \( W = 20 \times 0\) \( W = 0J\) No work has been done because the movement is not in the direction of the force. The weight acts downwards but the movement was horizontal. |