Magnetism Questions

A $2\text{amp}$ current is flowing through two different small circular copper coils having radii ratio $1:2$. The ratio of their respective magnetic moments will be:

If the magnetic dipole moment of an atom of diamagnetic material, paramagnetic material and ferromagnetic material are denoted by µd, µp and µf respectively, then :

A current carrying closed loop in the form of a right angle isosceles triangle $ABC$ is placed in a uniform magnetic field acting along $AB$. If the magnetic force on the arm $BC$ is $\vec{F}$, the force on the arm $AC$ is:

There are four light-weight-rod samples, $A,B,C,D$ separately suspended by threads. A bar magnet is slowly brought near each sample and the following observations are noted: (i) $A$ is feebly repelled (ii) $B$ is feebly attracted (iii) $C$ is strongly attracted (iv) $D$ remains unaffected. Which one of the following is true?

A uniform electric field and a uniform magnetic field are acting along the same direction in certain region. If an electron is projected in the region such that its velocity is pointed along direction of fields, then the electron:

A compass needle which is allowed to move in a horizontal plane is taken to a geomagnetic pole. It:

A conducting circular loop is placed in a uniform magnetic field, $B=0.025\text{ T}$ with its plane perpendicular to the loop. The radius of the loop is made to shrink at a constant rate of $1{\text{ mms}}^{-1}$. The induced emf when the radius is $2\text{ cm}$ is:

A $220\text{-volt}$ input is supplied to a transformer. The output circuit draws a current of $2.0\text{ ampere}$ at $440\text{ volts}$. If the efficiency of the transformer is $80\%$, the current drawn by the primary windings of the transformer is:

Charge $q$ is spread on a ring of radius $R$ rotating at frequency $f$. Magnetic induction at center is:

A bar magnet ($M=0.4{\text{JT}}^{-1}$) is in field $B=0.16\text{T}$. Potential energy in stable equilibrium is:

A square loop ($I$) is near a long wire ($I_1$) as shown. The loop experiences:

Electromagnets are made of soft iron because soft iron has:

A proton released from rest starts with acceleration $a_0$ towards west. When projected towards north with speed $v_0$, it moves with initial acceleration $3a_0$ towards west. The electric and magnetic fields in the room are:

A current loop in a magnetic field:

A bar magnet of length $l$ and magnetic dipole moment $M$ is bent in the form of an arc subtending $60^{\circ }$ at the center. The new magnetic dipole moment will be:

Following figures show the arrangement of bar magnets in different configurations. Each magnet has magnetic dipole moment $\vec{m}$. Which configuration has highest net magnetic dipole moment?

Two identical long conducting wires $AOB$ and $COD$ are placed at right angle to each other, with one above other such that '$O$ ' is their common point. The wires carry $I_1$ and $I_2$ currents, respectively. Point '$P$ ' is lying at distance '$d$ ' from '$O$ ' along a direction perpendicular to the plane containing the wires. The magnetic field at point '$P$ ' will be:

A rectangular coil of length $0.12\text{m}$ and width $0.1\text{m}$ having $50$ turns of wire is suspended vertically in a uniform magnetic field of strength $0.2{\text{Weber/m}}^2$. The coil carries a current of $2\text{A}$. If the plane of the coil is inclined at an angle of $30^{\circ }$ with the direction of the field, the torque required to keep the coil in stable equilibrium will be:

A proton and an alpha particle both enter a region of uniform magnetic field $B$, moving at right angles to the field $B$. If the radius of circular orbits for both the particles is equal and the kinetic energy acquired by proton is $1\text{MeV}$, the energy acquired by the alpha particle will be:

A particle of mass $m$, charge $Q$ and kinetic energy $T$ enters a transverse uniform magnetic field of induction $\vec{B}$. After $3$ seconds the kinetic energy of the particle will be:

A coil in the shape of an equilateral triangle of side l is suspended between the pole pieces of a permanent magnet such that is in plane of the coil. If due to a current i in the triangle a torque τ acts on it, the side l of the triangle is :

A very long straight wire carries a current I. At the instant when a charge + Q at point P has velocity , as shown, the force on the charge is :

The magnetic moment $(\mu )$ of a revolving electron around the nucleus varies with principal quantum number $n$ as:

A magnet is made to oscillate with a particular frequency, passing through a coil as shown in figure. The time variation of the magnitude of e.m.f. generated across the coil during one cycle is:

Nickel shows ferromagnetic property at room temperature. If the temperature is increased beyond Curie temperature, then it will show:

Under the influence of a uniform magnetic field a charged particle is moving in a circle of radius $R$ with constant speed $v$. The time period of the motion:

A charged particle (charge $q$) is moving in a circle of radius $R$ with uniform speed $v$. The associated magnetic moment $\mu$ is given by:

A beam of electrons passes un-deflected through mutually perpendicular electric and magnetic fields. If the electric field is switched off, and the same magnetic field is maintained, the electrons move:

A vibration magnetometer placed in magnetic meridian has a small bar magnet. The magnet executes oscillations with a time period of $2\text{ sec}$ in earth's horizontal magnetic field of $24\text{ microtesla}$. When a horizontal field of $18\text{ microtesla}$ is produced opposite to the earth's field by placing a current carrying wire, the new time period of magnet will be:

A closed loop $PQRS$ carrying a current is placed in a uniform magnetic field. If the magnetic forces on segments $PS$, $SR$, and $RQ$ are $F_1$, $F_2$, and $F_3$ respectively and are in the plane of the paper and along the directions shown, the force on the segment $QP$ is:

A circular disc of radius $0.2\text{meter}$ is placed in a uniform magnetic field of induction $\frac{1}{\pi }{\text{Wb/m}}^2$ in such a way that its axis makes an angle of $60^{\circ }$ with $\vec{B}$. The magnetic flux linked with the disc is:

Curie temperature is the temperature above which:

A bar magnet having a magnetic moment of $2\times 10^4{\text{JT}}^{-1}$ is free to rotate in a horizontal plane. A horizontal magnetic field $B=6\times 10^{-4}\text{T}$ exists in the space. The work done in taking the magnet slowly from a direction parallel to the field to a direction $60^{\circ }$ from the field is:

If a diamagnetic substance is brought near the north or the south pole of a bar magnet, it is:

A square current carrying loop is suspended in a uniform magnetic field acting in the plane of the loop. If the force on one arm of the loop is $\vec{F}$, the net force on the remaining three arms of the loop is:

A thin ring of radius $R\text{ meter}$ has charge $q\text{ coulomb}$ uniformly spread on it. The ring rotates about its axis with a constant frequency of $f\text{ revolutions/s}$. The value of magnetic induction in ${\text{Wb/m}}^2$ at the centre of the ring is: