Comprehension
A galvanometer is used to detect or/and measure small currents in an electrical circuit. It essentially works on the fact that a current-carrying coil experiences a deflecting torque when placed in a magnetic field. This deflection in the coil can be measured and it is related to the current flowing in the coil, the number of turns in the coil, area of the coil and the magnetic field. A hair spring attached to the coil provides a counter torque and helps in measuring the deflection. A galvanometer can be converted to an ammeter or a voltmeter of desired range by using suitable resistances.
Question: 1

The torque on the coil remains constant irrespective of the coil's orientation during rotation due to

Show Hint

A radial magnetic field ensures \[ \tau = NBAI \] and makes galvanometer deflection directly proportional to current.
Updated On: Jul 2, 2026
  • use of soft iron core which increases the magnetic field.
  • radial magnetic field
  • hair spring which provides the counter torque
  • eddy current in the iron core which causes damping
Show Solution

The Correct Option is B

Solution and Explanation

Was this answer helpful?
0
Question: 2

The best way to increase current sensitivity of a galvanometer is by

Show Hint

Current sensitivity: \[ S_i=\frac{NBA}{C} \] Increase \(N\), \(B\), \(A\) and decrease \(C\) to obtain higher sensitivity.
Updated On: Jul 2, 2026
  • increasing number of turns of the coil
  • increasing area of coil and magnetic field strength
  • decreasing area of coil and magnetic field strength
  • increasing torsional constant of the hair spring
Show Solution

The Correct Option is B

Solution and Explanation

Was this answer helpful?
0
Question: 3

A moving coil galvanometer has a coil with area \(4.0\times10^{-3}\,\text{m}^2\) and number of turns \(50\). The coil is rotating in a magnetic field of \(0.25\,\text{T}\). The torque acting on the coil when a current of \(5\,\text{A}\) passes through it is

Show Hint

For a radial magnetic field, \[ \tau = NBAI. \] Always use this formula directly for torque calculations in galvanometers.
Updated On: Jul 2, 2026
  • \(1.0\,\text{N m}\)
  • \(2.0\,\text{N m}\)
  • \(0.50\,\text{N m}\)
  • \(0.25\,\text{N m}\)
Show Solution

The Correct Option is D

Solution and Explanation

Was this answer helpful?
0
Question: 4

A galvanometer coil has a resistance of \(15\,\Omega\) and the meter shows full scale deflection for a current of \(3\,\text{mA}\). The value of resistance required to convert it into a voltmeter of range \((0-12\,V)\) is

Show Hint

To convert a galvanometer into a voltmeter, \[ R=\frac{V}{I_g}-G \] where \(R\) is connected in series with the galvanometer.
Updated On: Jul 2, 2026
  • \(4015\,\Omega\)
  • \(3985\,\Omega\)
  • \(415\,\Omega\)
  • \(385\,\Omega\)
Show Solution

The Correct Option is B

Solution and Explanation

Was this answer helpful?
0
Question: 5

A galvanometer with coil of resistance \(20\,\Omega\) shows full scale deflection for a current of \(5\,\text{mA}\). To convert it into an ammeter of range \((0-10\,A)\), a resistance of

Show Hint

To convert a galvanometer into an ammeter, a low resistance called shunt is connected in parallel. \[ S=\frac{I_gG}{I-I_g} \]
Updated On: Jul 2, 2026
  • \(0.05\,\Omega\) should be connected in series with it.
  • \(0.05\,\Omega\) should be connected in parallel with it.
  • \(0.01\,\Omega\) should be connected in parallel with it.
  • \(0.01\,\Omega\) should be connected in series with it.
Show Solution

The Correct Option is C

Solution and Explanation

Was this answer helpful?
0

Top Questions on The Moving Coil Galvanometer

Questions Asked in CBSE Class XII exam