Class 12 Moving Charges And Magnetism CBSE Questions & Answers

Class 12 · Moving Charges And Magnetism

This is Physics Class 12 Moving Charges and Magnetism CBSE Questions & Answers. There are 15 questions in this test with each question having around four answer choices.

Questions & Answers

1
The magnetic induction at centre O is
Question 1 figure 1
  • A
    \(\frac{\mu_o I}{2r}\)
  • B
    \(\frac{\mu_o I}{4\pi r}\)
  • C
    D .\(\frac{\mu_o I}{r}\)
  • D
    \(\frac{\mu_o I}{4r}\)
    Correct
2
protons move parallel to each other with equal speeds 3 x 105 ms-1. The ratio of magnetic and electric force between them is
  • A
    D . 1
  • B
    \({\rm{1}}{0^{ - {\rm{9}}}}\)
  • C
    \({\rm{1}}{0^{ - {\rm{6}}}}\)
    Correct
  • D
    \({\rm{1}}{0^{ - {\rm{3}}}}\)
3
long straight wires are connected by a circular section which has radius R. All the three segments lie in same plane and carry a current I. The magnetic induction at centre O of the circular segment is
Question 3 figure 1
  • A
    \(\frac{\mu_o I.\alpha}{4\pi r}\)
    Correct
  • B
    \(\frac{\alpha \mu_o I}{r}\)
  • C
    D .\(\frac{\alpha \mu_o I}{2\pi r}\)
  • D
    \(\frac{\mu_o I}{4\pi r}\)
4
ABCD is a circular coil of non-insulated thin uniform conductor. Conductors pa and qc are very long straight parallel wires, tangential to the coil at points a and c. Find magnetic induction at centre of coil when a current of 5 A is passing thereby. Radius of coil is 10 cm
Question 4 figure 1
  • A
    \({\rm{2 }} \times {\rm{1}}{0^{ - {\rm{5}}}}{\rm{T}}\)
  • B
    None of these
  • C
    \({\rm{1}}{0^{ - {\rm{5}}}}{\rm{T}}\)
    Correct
  • D
    \(0.{\rm{5 }} \times {\rm{ 1}}{0^{ - {\rm{5}}}}{\rm{T}}\)
5
An ammeter has resistance \({{\rm{R}}^{\rm{o}}}\) and range I. What resistance should be connected in parallel to it with increase the range to nI
  • A
    None of these
  • B
    \(\frac{R_o}{n}\)
  • C
    \(\frac{R_o}{n+1}\)
  • D
    \(\frac{R_o}{n-1}\)
    Correct
6
A voltmeter has range V. What resistance should be connected in series with it to increase its range to nV. Initial resistance is R0
  • A
    \(\left( {{\rm{n}} + {\rm{1}}} \right){{\rm{R}}_{\rm{o}}}\)
  • B
    \(\frac{R_o}{n}\)
  • C
    \({\rm{n}}{{\rm{R}}_{^{\rm{o}}}}\)
  • D
    \(\left( {{\rm{n}} - {\rm{1}}} \right){{\rm{R}}_{\rm{o}}}\)
    Correct
7
An electron is revolving around a proton in a circular orbit of diameter 0.1 nm. It produces a magnetic field of 14 \({\rm{Wb}}{{\rm{m}}^{\rm{2}}}\) at the proton. What is angular speed of the electron?
  • A
    \({\rm{4}}.{\rm{4}} \times {\rm{ 1}}{0^{{\rm{16}}}}{\rm{rad }}{{\rm{s}}^{ - {\rm{1}}}}\)
    Correct
  • B
    \({\rm{8}}.{\rm{8}} \times {\rm{ 1}}{0^{{\rm{16}}}}{\rm{rad }}{{\rm{s}}^{ - {\rm{1}}}}\)
  • C
    \({\rm{6}}.{\rm{4}} \times {\rm{ 1}}{0^{{\rm{16}}}}{\rm{rad }}{{\rm{s}}^{ - {\rm{1}}}}\)
  • D
    \({\rm{1}}.{\rm{4}} \times {\rm{ 1}}{0^{{\rm{16}}}}{\rm{rad }}{{\rm{s}}^{ - {\rm{1}}}}\)
8
A magnetic dipole is placed in two magnetic fields B and \({{\rm{B}}_{\rm{o}}}\) . It is in equilibrium making an angle \(\theta \) with direction of field B, then
Question 8 figure 1
  • A
    \({\rm{B }} = {\rm{ }}{{\rm{B}}_{\rm{o}}}\)
  • B
    \({\rm{B sin}}\theta {\rm{ }} = {\rm{ }}{{\rm{B}}_{\rm{o}}}{\rm{cos}}\theta \)
    Correct
  • C
    \({\rm{B }} = {\rm{ }}{{\rm{B}}_{\rm{o}}}{\rm{tan}}\theta \)
  • D
    \({\rm{B cos}}\theta {\rm{ }} = {\rm{ }}{{\rm{B}}_{\rm{o}}}{\rm{sin}}\theta \)
9
What is magnetic field in the empty space enclosed by toroidal solenoid of radius R?
  • A
    \(\frac{\mu_o }{4\pi}\).\(\frac{2 I}{R}\)
  • B
    Infinity
  • C
    \(\mu {\rm{ nI}}\)
  • D
    Zero
    Correct
10
The ratio of magnetic induction on the axis of a straight long current carrying solenoid at a point on end to that at the centre of solenoid is
  • A
    1 : 1
  • B
    1 : 2
  • C
    \(\sqrt{2}\) : 1
  • D
    2 : 1
    Correct
11
A ring of radius r is uniformly charged with charge q. It is rotated with angular velocity ω, then magnetic moment developed by the ring is
  • A
    \(\frac{qr^2\omega}{2}\)
    Correct
  • B
    \(\frac{2}{qr^2\omega ^2}\)
  • C
    \(\frac{q}{r^2\omega ^2}\)
  • D
    \(\frac{q\omega}{2r^2}\)
12
If only \({\rm{2}}\% \)of the current is to pass through a galvanometer of resistance G, then resistance of shunt will be
  • A
    50 G
  • B
    \(\frac{G}{49}\)
    Correct
  • C
    49 G
  • D
    \(\frac{G}{50}\)
13
An electron is shot into a liquid placed in a uniform magnetic field, in a plane perpendicular to magnetic field, then
  • A
    the kinetic energy of electron remains same
  • B
    the trajectory of electron is circular
  • C
    its revolution frequency decreases.
  • D
    trajectory is an inward winding spiral
    Correct
14
A galvanometer having 30 divisions has a current sensitivity of \({\rm{2}}0{\rm{ }}\mu {\rm{A}}/{\rm{div}}\). It has a resistance of 25 ohm. How will you convert it into an ammeter measuring upto 1 ampere. Find the shunt to be used
  • A
    0.15 \(\Omega \)
  • B
    0.030 \(\Omega \)
  • C
    0.015 \(\Omega \)
    Correct
  • D
    0.30 \(\Omega \)
15
A voltmeter has a range O-V with a series resistance of R ohm. With a series resistance of 2R, its range is O-V then
  • A
    \({\rm{V }} > {\rm{ 2V}}\)
  • B
    V = 2V
  • C
    \({\rm{V }} \ge {\rm{ 2V}}\)
  • D
    \({\rm{V }} < {\rm{ 2V}}\)
    Correct