To protect galvanometer from possible damages due to large current, which of the following should be connected to its coil:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → Low resistance wire in parallel
A moving-coil galvanometer is damaged by a large current through its coil. A shunt, a small resistance \( r_s \) in parallel with the coil, takes most of the current. Parallel branches share the current in inverse proportion to their resistances:
\( \displaystyle I_G = I\,\frac{r_s}{R_G + r_s} \)
When \( r_s \ll R_G \), \( I_G \) is only a small fraction of the total current I.
Why the other options are incorrect
Option (1) Low resistance wire in series — Incorrect. A series resistor does not divide the current: the whole current still passes through the coil, and a small series resistance hardly changes it.
Option (2) High resistance wire in series — Incorrect. This lowers the current in the whole circuit, but it is the arrangement of a voltmeter, not a protection that still lets the galvanometer measure a large current.
Option (3) High resistance wire in parallel — Incorrect. A large resistance in parallel takes almost no current, so nearly all the current still goes through the coil.
Note: The same question was also asked in CUET (UG) 2023 on 20-06-2023 (Slot 3).
NCERT (2026-27):
The Moving Coil Galvanometer – “… (i) Galvanometer is a very sensitive device, it gives a full- scale deflection for a current of the order of μA. … To overcome these difficulties, one attaches a small resistance rs, called shunt resistance, in parallel with the galvanometer coil; so that most of the current passes through the shunt.”