To convert a galvanometer into an ammeter, one should connect :

The correct answer is Option (3) → low resistance in parallel with galvanometer

An ammeter is connected in series in a circuit, so it must have a very low resistance and must carry a large current without damage. A galvanometer gives full-scale deflection for a very small current \( I_g \). A low resistance (shunt) \( r_s \) in parallel with it carries most of the current, so only \( I_g \) passes through the galvanometer.

    \( \displaystyle r_s = \frac{I_g\,G}{I - I_g} \)

Here \( G \) is the galvanometer resistance and \( I \) the full-scale current of the ammeter.

Option (1) high resistance in series with galvanometer — Incorrect. A high resistance in series converts the galvanometer into a voltmeter.

Option (2) low resistance in series with galvanometer — Incorrect. A resistance in series does not let the extra current bypass the galvanometer, and it raises the resistance of the meter.

Option (4) high resistance in parallel with galvanometer — Incorrect. A high resistance in parallel would take very little current, so almost all of it would still flow through the galvanometer.

NCERT (2026-27):
The Moving Coil Galvanometer – “… To overcome these difficulties, one attaches a small resistance r_s, called shunt resistance, in parallel with the galvanometer coil; so that most of the current passes through the shunt.”