List of top Physics Questions on Magnetic Effects of Current and Magnetism asked in CBSE CLASS XII

(I) Write Ampere’s circuital law in mathematical form and explain the terms used.
(II) As the current-carrying solenoid is made longer, the magnetic field produced outside it approaches zero. Why?
(III) A flexible loop of irregular shape carrying current, when located in an external magnetic field, changes to a circular shape. Give reason.

A 1 cm segment of a wire lying along the x-axis carries a current of 0.5 A along the \( +x \)-direction. A magnetic field \( \mathbf{B} = (0.4 \, \text{mT}) \hat{j} + (0.6 \, \text{mT}) \hat{k} \) is switched on in the region. The force acting on the segment is:

A rectangular loop carries a current of 1 A. A straight long wire carrying 2 A current is kept near the loop in the same plane as shown in the figure.

Find:
(i) the torque acting on the loop, and
(ii) the magnitude and direction of the net force on the loop.

Write vector form of Biot–Savart law.

The value of magnetic field at point \( O \) in the given figure is:

Two insulated long straight wires, each carrying \( 2.0 \ \text{A} \) current are kept along \( xx' \) and \( yy' \) axes as shown in the figure. Find the magnitude and direction of the resultant magnetic field at point \( P(4\,\text{m},\,5\,\text{m}) \).

A 1 cm segment of a wire lying along the x-axis carries current of \( 0.5 \, A \) along the \( +x \)-direction. A magnetic field \( \vec{B} = (0.4 \, \text{mT}) \hat{j} + (0.6 \, \text{mT}) \hat{k} \) is switched on, in the region. The force acting on the segment is:

Derive an expression for the torque acting on a rectangular current loop suspended in a uniform magnetic field.

A current carrying circular loop of area \( A \) produces a magnetic field \( B \) at its centre. Show that the magnetic moment of the loop is: \[ \mu = \frac{2BA}{\mu_0} \sqrt{\frac{A}{\pi}} \]

A proton moving with velocity \( \vec{V} \) in a non-uniform magnetic field traces a path as shown in the figure. The path followed by the proton is always in the plane of the paper. What is the direction of the magnetic field in the region near points P, Q, and R? What can you say about relative magnitude of magnetic fields at these points?

Two long insulated straight wires carrying currents of \( 3A \) and \( 5A \) are arranged in the XY plane as shown in the figure. Find the magnitude and direction of the net magnetic fields at points \( P_1(2m, 2m) \) and \( P_2(-1m, 1m) \). 

An electron moving with a velocity \( \vec{v} = (1.0 \times 10^7 \, \text{m/s}) \hat{i} + (0.5 \times 10^7 \, \text{m/s}) \hat{j} \) enters a region of uniform magnetic field \( \vec{B} = (0.5 \, \text{mT}) \hat{j} \). Find the radius of the circular path described by it. While rotating, does the electron trace a linear path too? If so, calculate the linear distance covered by it during the period of one revolution.}

Assertion (A): The energy of a charged particle moving in a magnetic field does not change. % Reason (R) Reason (R): It is because the work done by the magnetic force on the charge moving in a magnetic field is zero.

A proton with kinetic energy $1.3384 \times 10^{-14 \, \text{J}$ moving horizontally from north to south, enters a uniform magnetic field $B = 2.0 \, \text{mT}$ directed eastward. Calculate:}
\textbf{(a) the speed of the proton,

Assertion (A): Two long parallel wires, freely suspended and connected in series to a battery, move apart.
Reason (R):Two wires carrying current in opposite directions repel each other.

A $10 \, \text{cm$ long wire lies along $y$-axis. It carries a current of $1.0 \, \text{A}$ in positive $y$-direction. A magnetic field $\vec{B} = (5 \, \text{mT}) \, \hat{j} - (8 \, \text{mT}) \, \hat{k}$ exists in the region. The force on the wire is:}

An infinite straight conductor is kept along \( X'X \) axis and carries a current \( I \). A charge \( q \) at point \( P(0, r) \) starts moving with velocity \( \vec{v} = v_0 \, \hat{j} \) as shown in figure. Find the direction and magnitude of force initially experienced by the charge. 

Two long straight parallel conductors A and B, kept at a distance \( r \), carry current \( I \) in opposite directions. A third identical conductor C, kept at a distance \( \frac{r}{3} \) from A, carries current \( I_1 \) in the same direction as A. The net magnetic force on unit length of C is:

A particle of mass \( m \) and charge \( q \) is moving with velocity \( \mathbf{v} = v_x \hat{i} + v_y \hat{j} \). If it is subjected to a magnetic field \( \mathbf{B} = B_0 \hat{i} \), it will move in a:

Define mutual inductance. Write its SI unit.

A straight wire is kept horizontally along the east-west direction. If a steady current flows in the wire from east to west, the magnetic field at a point above the wire will point towards: