A student tests a diode by connecting it into a circuit one way round and then the other way round. In one connection the diode is in its forward direction and in the other it is in its reverse direction. The student adjusts the supply so that the potential difference across the diode is the same in both tests.
| Connection | Potential difference across diode in V | Current through diode in mA |
|---|---|---|
| P | 0.75 | 20 |
| Q | 0.75 | 0.002 |
What do these results show about the diode?
The resistance is much higher for connection P, so P is the reverse direction.
The resistance is zero for connection Q because the current there is almost zero.
The resistance is much lower for connection P, so P is the forward direction.
The resistance is the same for both connections because the potential difference is unchanged.
82 exam-style questions on AQA GCSE Physics 2.1 Current, potential difference and resistance, covering 2.1.1 Standard circuit diagram symbols, 2.1.2 Electrical charge and current, 2.1.3 Current, resistance and potential difference, and 2.1.4 Resistors. Each one has a worked solution and a mark scheme showing where the marks go.