Magnetic Field

Q. What is the flux through a cube of side $a$ if a point charge of $q$ is at one of its corner?

1. $\frac{2q}{{\epsilon }_0}$
2. $\frac{q}{8{\epsilon }_0}$
3. $\frac{q}{{\epsilon }_0}$
4. $\frac{3q{a}^2}{{\epsilon }_0}$

Q.

What is the relation between relative permeability and magnetic susceptibility?

Q. Difference between electric field and magnetic field

Q.

The dimensional formula of magnetic flux is

Q.

State Tangent Law in magnetism.

Q. A magnetic needle is kept in a non-uniform magnetic field. It experiences:

1. A force only but not a torque
2. Neither a torque nor a force
3. A force and torque both
4. A torque only but not a force

Q. A current carrying square loop is placed near an infinitely long current carrying wire as shown in figure. The torque acting on the loop is

1. $\frac{{\mu }_0}{2\pi }\left(\frac{i_1{i}_{2}a}{2}\right)$
2. $\left(\frac{{\mu }_0{i}_1{i}_{2}a}{2\pi }\right)$
3. $\left(\frac{{\mu }_0{i}_1{i}_{2}a}{2\pi }\right)\ln 2$
4. zero

Q. The magnetic susceptibility of a rod is $499.$ The absolute permeability of vacuum is ${\mu }_0=4\pi \times {10}^{-7}{\text{Hm}}^{-1}.$ The absolute permeability of the material of the rod is-

1. $4\pi \times {10}^{-4}{\text{Hm}}^{-1}$
2. $3\pi \times {10}^{-4}{\text{Hm}}^{-1}$
3. $2\pi \times {10}^{-4}{\text{Hm}}^{-1}$
4. $\pi \times {10}^{-4}{\text{Hm}}^{-1}$

Q. A plane electromagnetic wave travels in free space along the x-direction. The electric field component of the wave at a particular point of space and time is $E=6V{m}^{-1}$ along y-direction. Its corresponding magnetic field component, $B$ would be

1. $6\times {10}^{-8}T$ along z-direction
2. $6\times {10}^{-8}T$ along x-direction
3. $2\times {10}^{-8}T$ along z-direction
4. $2\times {10}^{-8}T$ along y-direction

Q.

The work done in turning a magnet of magnetic moment M by an angle of ${90}^{\circ }$ from the meridian is n times the corresponding work done to turn it through an angle of ${60}^{\circ }$.

1. $n=1$
2. $n=\frac{1}{2}$
3. $n=2$
4. $n=\frac{1}{4}$

Q.

State four characteristics of the magnetic lines of force.

Q. Ratio of magnetic dipole moment to the angularmomentum for hydrogen like atoms is (e and m are electronic charge and mass respectively) -e/m -2e/m -e/2m -e/4

Q. A light beam of wavelength $500\text{nm}$ is incident on a metal having work function of $1.25\text{eV}$, placed in a magnetic field of intensity $B$. The electrons emitted perpendicular to the magnetic field $B$, with maximum kinetic energy, are bent into a circular arc of radius $30\text{cm}$. The value of $B$ is $\times {10}^{-7}\text{T}$.
Given $hc=20\times {10}^{-26}\text{Jm}$, mass of electron $m_e=9\times {10}^{-31}\text{kg}$

Q.

What is Magnetic Field and its Unit

Q.

Which of the following substances are strongly attracted by magnetic fields?

1. Ferromagnetic Material

2. Diamagnetic Material

3. Paramagnetic

4. None of the above

Q. PARAGRAPH
In electromagnetic theory, the electric and magnetic phenomena are related to each other. Therefore, the dimensions of electric and magnetic quantities must also be related to each other. In the questions below, $\left[E\right]$ and [𝐵] stand for dimensions of electric and magnetic fields respectively, while $\left[{\epsilon }_0\right]$ and $\left[{\mu }_0\right]$ stand for dimensions of the permittivity and permeability of free space respectively. $\left[L\right]$ and $\left[T\right]$ are dimensions of length and time respectively. All the quantities are given in SI units.


The relation between [𝐸] and [𝐵] is

1. $\left[E\right]=\left[B\right]\left[L\right]\left[T\right]$
2. $\left[E\right]=\left[B\right]\left[L{]}^{-1}\right[T]$
3. $\left[E\right]=\left[B\right]\left[L\right][T{]}^{-1}$
4. $\left[E\right]=\left[B\right]\left[L{]}^{-1}\right[T{]}^{-1}$

Q.

What are the properties of a magnet ?

Q. A thin flexible wire of length $L$ is connected to two adjacent fixed points and carries a current $I$ in the clockwise direction as shown in figure. When the system is put in a uniform magnetic field of strength $B$, going into plane of paper, the tension developed in the wire will be:

1. $IBL$
2. $\frac{IBL}{\pi }$
3. $\frac{IBL}{2\pi }$
4. $\frac{IBL}{4\pi }$

Q.

What is Weber in physics?

Q. A liquid wets glass. Its angle of contact with glass is:

1. $\pi$
2. Less than $\frac{\pi }{2}$
3. $\frac{\pi }{2}$
   
4. $\frac{3\pi }{2}$
   

Q. A wire $\text{abc}$ is carrying current $i$. It is bent as shown in the figure, and is placed in a uniform magnetic field of magnetic induction $B$. The length of $\text{ab}$ is $l$ and $\angle abc={45}^{\circ }$. The ratio of magnetic force on $\text{ab}$ to that on $\text{bc}$ is:

1. $\frac{1}{\sqrt{2}}$
2. $\sqrt{2}$
3. $1$
4. $\frac{2}{3}$

Q.

Why skin effect is shown by AC and not by DC?

Q. Two ions of masses $4\text{amu}$ and $16\text{amu}$ have charges $+2e$ and $+3e$ respectively. These ions pass through the region of constant magnetic field perpendicular to their motion. The kinetic energy of both ions is the same. Then:

1. lighter ion will be deflected less than heavier ion
2. no ion will be deflected
3. lighter ion will be deflected more than heavier ion
4. both ions will be deflected equally

Q.

A $50$turns circular coil has a radius of $3cm$, it is kept in a magnetic field acting normal to the area of the coil. The magnetic field $B$ increased from $0.10tesla$ to $0.35tesla$ in $2milliseconds$. The average induced e.m.f. in the coils is

1. $1.77volts$

2. $17.7volts$

3. $177volts$

4. $0.177volts$

Q.

When a charged particle enters a magnetic field in a direction perpendicular to the field, which one of the following does not change?

1. energy of the particle.

2. momentum of the particle.

3. mass of the particle.

4. velocity of the particle.

Q.

A uniform but time varying magnetic field B(t) exists in a circular region of radius a and is directed into the plane of the paper as shown in Fig. 25.21.

The magnitude of the induced electric field at point P at a distance r from the centre of the circular region

1. decreases as $\frac{1}{r}$

2. decreases as $\frac{1}{r^2}$.

3. is zero

4. increases as r

Q.

In a permanent magnet at room temperature

1. domains are partially aligned.

2. domains are all perfectly aligned.

3. magnetic moment of each molecule is zero.

4. the individual molecules have non-zero magnetic moment which are all perfectly aligned.

Q.

Where are the poles of a bar magnet located?

Q. Kirchhoff’s loop law is based on the conservation of

​​​​​​​$[$0.77 Mark$]$

1. Charge
2. Momentum
3. Angular Momentum
4. Energy

Q.

The relation between $Weber$ and $Tesla$is

1. $1Wb=1T$

2. $1Wb=1T\times 1m^2$

3. $1Wb=1T\times 1m^{-2}$

4. $1W{b}^2=1T\times 1m^2$