Question

Resistance of an ideal Ammeter is
A. Infinite
B. Very high
C. Small
D. Zero

Answer 1

- Hint: An ammeter is a device that is connected in circuit to calculate the amount of current flowing through the circuit. Ideal ammeter is the case where the ammeter reading is exactly equal to the total current in the circuit.

Complete step-by-step solution -

An ammeter is a device that is connected in series to the circuit so that we can calculate the total current passing through the circuit by the reading of the ammeter. Since the ammeter is connected in series, the equivalent resistance of the circuit with ammeter will be more than the circuit resistance thus decreasing the current flow in the circuit. Hence, an error is produced.
However, to minimize this error, generally ammeters are provided with very less resistance, say, negligible resistance. Practically, a conducting material with zero resistance is impossible to find. So, we imagine an ideal ammeter that allows complete flow of current without affecting the resistance of the equivalent circuit.
So, we can conclude that the ammeter provides zero resistance. The correct answer is option D. Zero.

Note: We will now solve this question experimentally.
Formula for equivalent resistance(R) of a circuit in which two conductors with resistances X and Y are connected in parallel is given by,
R = X + Y.
An ideal ammeter doesn't change the equivalent resistance. Hence, its resistance will be zero so that we do not get error while calculating current through the circuit using ammeter and the equivalent resistance is exactly equal to the original circuit resistance. Thus, the correct answer is option D. Zero.