Question

A moving coil ammeter is to be adapted to detect small alternating currents. Which of the diagrams shows how a diode could be connected in order to make conversion?

Answer 1

The current must pass through the meter in the direction + to-only.

Complete step by step solution:
Initial Elimination,
The current must pass through the meter in the direction + to-only.
The diodes in (a) and (b) will not stop the reverse current, so can be eliminated.

Final deduction,
The current must pass through the meter in the direction + to-only.

So (c) is the correct option.

Note: The moving current creates a temporary magnetic field around the coil that repels the magnetic field created by the permanent magnet. The strength of the magnetic field is directly related to the size of the current that flows through the coil.
An ammeter is a measuring instrument used to measure the current in a circuit.