9.3.1—Resistance
- Syllabus
- 9702–2028–2029
- Objective
- 9.3.1
- Level
- AS
Resistance measures opposition to current through the ratio of voltage to current
Resistance is R=V/I at an operating point, measured in ohms. It describes how much potential difference is needed for a given current.
For a non-ohmic device the ratio can change with voltage, current or temperature, so call it operating-point resistance when appropriate.
A component carrying 0.50 A at 4.0 V has resistance 8.0 Ω at that point.
Resistance is not “used up” by a component and is not necessarily constant for every material or device.
ConceptA-Level CAIE Physics AS