An ammeter should have very low resistance

The correct answer is Option (4) → so that it may not change the value of the actual current in the circuit

An ammeter is connected in series, so its resistance \( R_A \) adds to the resistance of the circuit. A large \( R_A \) would reduce the very current it is meant to measure; a very low resistance leaves the current practically unchanged.

    \( \displaystyle I = \frac{E}{R + R_A} \approx \frac{E}{R} \quad (R_A \ll R) \)

Option (1) to show large deflection — Incorrect. The deflection depends on the current through the coil and on the sensitivity of the galvanometer, not on the low resistance of the ammeter.

Option (2) to generate less heat — Incorrect. Less heating is only a side effect of the low resistance, not the reason it is required.

Option (3) to protect the galvanometer from damage — Incorrect. The shunt protects the coil by carrying most of the current, but the low resistance of the ammeter as a whole is needed so that the circuit is not disturbed.

Option (4) so that it may not change the value of the actual current in the circuit — Correct. With a negligible resistance in series, the circuit current is the same as without the ammeter, so it reads the actual current.

NCERT (2026-27):
The Moving Coil Galvanometer – “… (ii) For measuring currents, the galvanometer has to be connected in series, and as it has a large resistance, this will change the value of the current in the circuit.”

The Moving Coil Galvanometer – “… If r_s has small value, in relation to the resistance of the rest of the circuit R_c, the effect of introducing the measuring instrument is also small and negligible.”