# Test – Important Questions – Chapter 4 – Moving Charges & Magnetism – Class 12 Physics

1.Write the underlying principle of a moving coil galvanometer. (Delhi 2015)

2. An electron is moving along +ve x-axis in the presence of uniform magnetic field along +ve y-axis. What is the direction of force acting on it?

3. How is the magnetic field inside a given solenoid made strong? (All India 2011)

4. Using Ampere’s circuital law, obtain an expression for the magnetic field along the axis of a current carrying solenoid of length l and having N number of turns. (All India 2008)

5. Write the expression for Lorentz magnetic force on a particle of charge ‘q’ moving with velocity ‘v’ in a magnetic field ‘B’. Show that no work is done by this force on the charged particle. (All India 2011)

6. A steady current (I1) flows through a long straight wire. Another wire carrying steady current (I2) in the same direction is kept close and parallel to the first wire. Show with the help of a diagram how the magnetic field due to the current I1 exerts a magnetic force on the second wire. Write the expression for this force. (All India 2011)

7. Using Ampere’s circuital law, obtain the expression for the magnetic field due to a long solenoid at a point inside the solenoid on its axis. (All India 2011)

8. Two identical circular wires P and Q each of radius R and carrying current ‘I’ are kept in perpendicular planes such that they have a common centre as shown in the figure. Find the magnitude and direction of the net magnetic field at the common centre of the two coils. (Delhi 2011).

9. Two identical circular loops, P and Q, each of radius r and carrying equal currents are kept in the parallel planes having a common axis passing through O. The direction of current in P is clockwise and in Q is anti-clockwise as seen from O which is equidistant from the loops P and Q. Find the magnitude of the net magnetic field at O. (Delhi 2011)

10. A circular coil of closely wound N turns and radius r carries a current I. Write the expressions for the following:

(1) the magnetic field at its centre.

(2) the magnetic moment of this coil (All India 2011)

11. State the underlying principle of a cyclotron. Write briefly how this machine is used to accelerate charged particles to high energies. (Delhi 2014)

12. A rectangular coil of sides ‘V and ‘b’ carrying a current I is subjected to a uniform magnetic field ‘B’ acting perpendicular to its plane. Obtain the expression for the torque acting on it. (Comptt. Delhi 2014)

13. (i) State Biot – Savart law in vector form expressing the magnetic field due to an element ‘dl’ carrying current I at a distance ‘r’ from the element.

(ii) Write the expression for the magnitude of the magnetic field at the centre of a circular loop of radius r carrying a steady current I. Draw the field lines due to the current loop. (Comptt. All India 2014)

14. A proton and an alpha particle having the same kinetic energy are, in turn, passed through a region of uniform magnetic field, acting normal to the plane of the paper and travel in circular paths. Deduce the ratio of the radii of the circular paths described by them. (Comptt. Delhi 2015)

15. Derive the expression for force per unit length between two long straight parallel current carrying conductors. Hence define one ampere. (Delhi 2015)

error: Content is protected !!