AIIMS Physics Moving Charges and Magnetism Class 12 Questions

A semi circular arc of radius r and a straight wire along the diameter, both are carrying same current i. Find out magnetic force per unit length on the small element P, which is at the centre of curvature.

A coil is placed in y-z plane making an angle of 30° with x-axis. The current through coil is I, and number of turns are N. If a magnetic field of strength ‘B’ is applied in positive x-direction, then find the torque experienced by the coil: (Radius of coil is R) (N = 100, I = 1 Å, R = 2m, B = 1/π T)

In the figure, find out the magnetic field at B (Given I = 2.5A, r = 5 cm)

Find force per unit length at P.

Find magnetic field at centre P if length of side of square loop is 20 cm.

In figure two parallel infinitely long current carrying wires are shown. If resultant magnetic field at A is zero, then determine current I₁.

The unit of magnetic flux is:

Two circular loops having same radius $[R = 10 \text{ cm}]$ and same current $\frac{7}{2} \text{ A}$ are placed along same axis as shown. If distance between their centre is $10 \text{ cm}$, find net magnetic field at point P.

Force on current carrying loop (Radius = R) in uniform magnetic (B) field which is at an angle 30º with the normal will be :

$\alpha$ particle is revolving in radius $r$ with frequency $f$ then find value of magnetic dipole moment.

In figure two parallel infinitely long current carrying wires are shown. If resultant magnetic field at point A is zero. Then determine current I.

Assertion : A charge particle is released from rest in magnetic field then it will move in circular path.

Reason : Work done by magnetic field is non zero.

Assertion: The kinetic energy does not change when a particle moves in uniform magnetic field.

Reason: The velocity of the particle is not affected by magnetic field.

Assertion: Paramagnetic substances get poorly attracted in magnetic field.

Reason : Because magnetic dipoles are aligned along external magnetic field weakly

At what distance for a long straight wire carrying a current of 12 Å will the magnetic field be equal to 3×10⁻⁵ Wb/m²?

Assertion : If a compass needle be kept at magnetic north pole of the earth, the compass needle may stay in any direction.

Reason : Dip needle will stay vertical at the north pole of earth.

Deuteron and an α particle move in same radius in a uniform magnetic ‘B’ field. If energy of deuteron is E₀ then find out the energy of α particle.

A long cylindrical wire carrying current of 10 amp. has radius of 5 mm, then find its magnetic field induction at a point 2 mm from the centre of the wire

2 long parallel wires which are 2 m apart carry current in the opposite direction but of same magnitude 2 amp, then find out the value of magnetic field intensity at the mid-point of the 2 wires and in the same plane.

‘Biot-Savart’ law of magnetism is analogous to:

A wire of length $3\text{ cm}$ has current $1\text{ amp}$. Find magnetic field at a perpendicular distance $1\text{ cm}$ from the centre of wire.

Consider the circular loop having current i and with central point O. The magnetic field at the central point is

If an electron of charge $e$ is moving parallel to a current carrying wire as shown in figure, then the force on the electron will be :

A magnetic material is placed in a non-uniform magnetic field which is oriented along z-axis having gradient = dH/dz, then force experienced by the material will be equal to

The earth's magnetic field lines resemble that of a dipole at the centre of the earth. If the magnetic moment of this dipole is close to $8 \times 10^{22}\text{ Am}^2$, the value of earth's magnetic field near the equator is close to (radius of the earth = $6.4 \times 10^6\text{ m}$)

A bar magnet has length $8\text{ cm}$. The magnetic field at a point at a distance $3\text{ cm}$ from the centre in the broad side-on position is found to be $4 \times 10^{-6}\text{ T}$. The pole strength of the magnet is:

Assertion: Magnetic field can not change K.E. moving charge.

Reason: Magnetic field can not change velocity vector.

Assertion : To protect any instrument from external magnetic field, it is put inside an iron body.

Reason : Iron has high permeability.

Assertion : Figure shows a current carrying circular loop. The magnetic field at the centre of loop is zero.

Reason : Magnetic field at the centre of loop is given by $B = \frac{\mu_0 ni}{2R}$

Assertion : The earth′s magnetic field is due to iron present in its core.

Reason : At a high temperature magnet losses its magnetism.

The angle of dip if dip needle oscillating in vertical plane makes 40 oscillations per minute in a magnetic meridian and 30 oscillations per minute in vertical plane at right angle to the magnetic meridian is

In the following questions, a statement of assertion is given followed by a corresponding statement of reason. Assertion: The magnetic field at the end of very long current carrying solenoid is half of that at the center. Reason: The focal length of lens does not depends on color of light used.

The magnetic field at the centre O of the arc shown in the figure is

The variation of magnetic susceptibility with the temperature of a ferromagnetic material can be plotted as

Assertion (A) A wire bent into an irregular shape with the points P and Q fixed. If a current I passed through the wire, then the area enclosed by the irregular portion of the wire increases.

Reason (R) Opposite currents carrying wires repel each other.

Assertion: Magnetic lines forms closed loops in nature. Reason: Mono-magnetic pole does not exist in nature.

Assertion: Magnetic field is useful in producing parallel beam of charged particle. Reason: Magnetic field inhibits the motion of charged particle moving across it.

A wire of mass 100 g, length 1 m and current 5 Å is balanced in mid air by a magnetic field B, then find the value of B.

A toroid with mean radius r₀ diameter 2a have N turns carrying current I. What is the magnetic field B inside the toroid?

Two wires carrying

Assertion: Magnetic force is always perpendicular to the magnetic field. Reason: Electric force is along the direction of electric field.

What is the dimensions of magnetic field B in terms of C (= coulomb), M, L, T?

A proton travels few distance in an electric field, then it enters a crossed magnetic field of 1 T and radius 0.2 m, Find the velocity of proton.

Magnetic field at a distance a from long current carrying wire is proportional to

When a positively charged particle enters into a uniform magnetic field with uniform velocity, its trajectory can be

(i) a straight line

(ii) a circle

(iii) a helix

An uncharged particle is moving with a velocity of v in non-uniform magnetic field as shown. Velocity v would be

Assertion: If a proton and an α-particle enter a uniform magnetic field perpendicularly with the same speed, the time period of revolution of α-particle is double that of proton. Reason: In a magnetic field, the period of revolution of a charged particle is directly proportional to the mass of the particle and is inversely proportional to charge of particle.

A current I₁ carrying wire AB is placed near another long wire CD carrying current I₂. If wire AB is free to move, it will have

Assertion : A charge, whether stationary or in motion produces a magnetic field around it. Reason : Moving charges produce only electric field in the surrounding space.

Two charges +q and -q are attached to the two ends of a light rod of length L, as shown in figure. The system is given a velocity v perpendicular to magnetic field B̅. The magnetic force on the system of charges and magnitude of force on one charge by the rod, are respectively