Question

The net resistance of an ammeter should be small to ensure that:
A. It does not get overheated
B. It does not draw excessive current to be measured
C. It can measure large current
D. It does not appreciably change the current to be measured

Answer 1

Hint: Ammeter is used to measure electric current and the net resistance of an ammeter should be small in quantity. Moreover, the more the current flows through, the better the reading would be obtained from the ammeter, and resistance is the ability of a material to resist the flow of current.

Complete answer:
Ammeter is the appliance which we use to measure electric current passing through a circuit. The resistance of a circuit is the ability of the material to resist the flow of the electric current or to oppose the flow of electric current passing through the circuit.
Thus, when there is resistance in a circuit, the current flown would be less, which is shown by the equation of the Ohm’s law as follows:
\[
V = IR \\
\therefore I \propto \dfrac{1}{R} \\ \]
Thus, as the resistance of the circuit increases, then the current in the circuit decreases, while if the resistance in the circuit decreases, then the current in the circuit increases. Thus, current and resistance are inversely proportional to each other. Now, for an ammeter, the net resistance of the ammeter should be less, and this is because as the resistance in the ammeter increases, it opposes the current more, and hence one will not be able to obtain the true value of the current flowing across the circuit.

Hence, option D is the correct answer.

Note:Shunt resistance is a device which is connected to an ammeter to extend its current calculating capacity by getting connected to a resistor in parallel and decreasing the capacity of the resistance. Thus, shunt resistance should have a value which decreases the resistance of the resistors when connected in parallel.