Magnetic Flux

Q.

What is meant by electric flux density?

Q. The magnetic induction at the center $\text{O}$ in the figure is,

1. $\frac{{\mu }_{0}I}{4}(\frac{1}{R_1}-\frac{1}{R_2})$
2. $\frac{{\mu }_{0}I}{4}(\frac{1}{R_1}+\frac{1}{R_2})$
3. $\frac{{\mu }_{0}I}{4}(R_1-R_2)$
4. $\frac{{\mu }_{0}I}{4}(R_1+R_2)$

Q. The variation of magnetic susceptibility $\left(\chi \right)$ with temperature for a diamagnetic substance is best represented by

1. 
2. 
3. 
4. 

Q. In Bohr's Model of hydrogen atom, the electron circulates around the nucleus in a path of radius $5.1\times {10}^{-11}\text{m}$ at a frequency of $6.8\times {10}^{15}\text{Hz}$. The value of magnetic field and equivalent magnetic moment will be

1. $15.4\text{T}$ and $8.9\times {10}^{-24}{\text{Am}}^2$
2. $18.4\text{T}$ and $9.8\times {10}^{-24}{\text{Am}}^2$
3. $13.4\text{T}$ and $8.9\times {10}^{-24}{\text{Am}}^2$
4. $18.4\text{T}$ and $8.9\times {10}^{-24}{\text{Am}}^2$

Q. Relative permittivity and permeability of a material is ${ϵ}_r$ and ${\mu }_r$, respectively. Which of the following values of these quantities are allowed for a diamagnetic material ?

1. ${ϵ}_r=0.5,{\mu }_r=1.5$
2. ${ϵ}_r=1.5,{\mu }_r=0.5$
3. ${ϵ}_r=0.5,{\mu }_r=0.5$
4. ${ϵ}_r=1.5,{\mu }_r=1.5$

Q. Gauss's law can help in the easy calculation of electric field due to:

1. moving charge only.
2. any charge configuration.
3. any symmetrical charge configuration.
4. some special symmetric charge configurations.

Q.

The direction of the equipotential surface is __________ to the uniform electric field lines.

Q. Consider a conducting wire of length $L$ bent in the form of a circle of radius $R$ and another conductor of length '$a$' ($a<<R$) bent in the form of a square. The two loops are then placed in the same plane such that the square loop is exactly at the centre of the circular loop. What will be the mutual inductance between the two loops?

1. ${\mu }_0\frac{\pi a^2}{L}$
2. ${\mu }_0\frac{\pi a^2}{16L}$
3. ${\mu }_0\frac{\pi a^2}{4L}$
4. ${\mu }_0\frac{a^2}{4\pi L}$

Q. A short bar magnet placed with its axis at ${30}^{\circ }$ with a uniform external magnetic field of $0.16\text{T}$ , experiences a torque of $0.032\text{Nm}.$ If the bar magnet is free to rotate, its potential energy when it is in stable and unstable equilibrium are-

1. $0.032\text{J};-0.032\text{J}$
2. $0.064\text{J};-0.128\text{J}$
3. $-0.032\text{J};0.032\text{J}$
4. $-0.064\text{J};0.064\text{J}$

Q. The variation of magnetic susceptibility $\chi$ with absolute temperature $T$, for a ferromagnetic material, is best shown by which of the following graphs?

1. 
2. 
3. 
4. 

Q.

The electric flux through an area dA for an electric field E is given by

Q.

Which of the following correctly describes the magnetic field near a long straight wire?

1. The field consists of straight lines perpendicular to the wire

2. The field consists of straight lines parallel to the wire

3. The field consists of radial lines originating from the wire

4. The field consists of concentric circles centered on the wire

Q.

How does the magnetic field around a magnet depend on the distance from the magnet?

Q. A square coil ${10}^{-2}{\text{m}}^2$ area is placed with its plane perpendicular to a uniform magnetic field of intensity ${10}^3{\text{Wb/m}}^2.$ The magnetic flux through the coil is

1. $10\text{Wb}$
2. ${10}^{-5}\text{Wb}$
3. ${10}^5\text{Wb}$
4. $100\text{Wb}$

Q. The magnetic flux $\left(\varphi \right)$ through a coil varies with time $t$ as shown in the diagram. Which graph best represents the variation of the e.m.f $E$ induced in the coil with time $t$ ?

1. 
2. 
3. 
4. 

Q. 110.There is a uniform electrostatic field in a region. The potential at various points on a small sphere centred at P, in the region, is found to vary between the limits 589.0 V to 589.8 V. What is the potential at a point on the sphere whose radius vector makes an angle 60^° with the direction of electric field? a)589.2 V b)589.6 V c)589.5 V d)589.4 V

Q.

What is the definition of electric field lines?

Q. The ratio of magnetic dipole moment to that of the angular momentum of an electron of mass $m\text{kg}$ and charge $e\text{C}.$ In Bohr's orbit of the hydrogen atom is-

1. $\frac{e}{m}$
2. $\frac{2e}{m}$
3. $\frac{e}{2m}$
4. ${\left(\frac{e}{m}\right)}^2$

Q. A uniform magnetic field $B$ exists in a region. An electron of charge $e$ is given velocity perpendicular to the magnetic field. Using, Bohr's quantization rule for angular momentum, the radius of the $n^{th}$ orbit is $\frac{nh}{k\pi eB}$, here $h$ is plank's constant. The value of $k$ is (Integer only)

Q.

The magnetic field in a coil of $100$turns and $40squarecm$area is increased from $1tesla$ to $6tesla$ in $2$ second. The magnetic field is perpendicular to the coil. The e.m.f. generated in it is

1. $104V$

2. $1.2V$

3. $1.0V$

4. ${10}^{-2}V$

Q. An electron orbiting around the nucleus of an atom

1. Has a magnetic dipole moment
2. Exerts an electric force on the nucleus equal to that on it by the nucleus
3. Does produce a magnetic induction at the nucleus
4. Has a net energy, whose magnitude is inversely proportional to its distance from the nucleus.

Q. Assertion $\left(A\right)$ : Magnetic moment of an atom is due to both, the orbital motion and spin motion of every electron.

Reason $\left(R\right)$ : A charged particle at rest produces a magnetic field.

1. Both $\left(A\right)$ and $\left(R\right)$ are true, $\left(R\right)$ is the correct explanation of $\left(A\right)$
2. Both $\left(A\right)$ and $\left(R\right)$ are true, $\left(R\right)$ is not the correct explanation of $\left(A\right)$
3. $\left(A\right)$ is true but $\left(R\right)$ is false.
4. $\left(A\right)$ is false but $\left(R\right)$ is true.

Q. A rectangular coil of $20$ turns and area of cross-section $25c{m}^2$ has a resistance of $100\Omega$. If a magnetic field which is perpendicular to the plane of coil changes at a rate of $1000T/s$ , the current in the coil is

1. $1A$
2. $50A$
3. $0.5A$
4. $5A$

Q. A uniform magnetic field is restricted within a region of radius $r$. The magnetic field changes with time at a rate $\frac{dB}{dt}$. The circular region containing magnetic field has a radius $r$. Loop $1$ of radius $R>>r$ encloses the region $r$ and Loop $2$ of radius $R$ is outside the region of magnetic field as shown in the figure. Then the e.m.f generated is,

1. Zero in loop $1$ and zero in loop $2$
2. $-\frac{\overrightarrow{dB}}{dt}\pi r^2$ in loop $1$ and $-\frac{\overrightarrow{dB}}{dt}\pi r^2$ in loop $2$
3. $-\frac{\overrightarrow{dB}}{dt}\pi R^2$ in loop $1$, zero in loop $2$
4. $-\frac{\overrightarrow{dB}}{dt}\pi r^2$ in loop $1$, zero in loop $2$

Q. If magnetic field strength at the center of a hydrogen atom caused by an electron moving along the first Bohr orbit is $\frac{x}{2}\text{T}$. The value of $x$ nearly is (integer only)

Q.

A thin wire loop carrying a current $I$ is placed in a uniform magnetic field $B$ pointing into the plane of the coil as shown in the figure. The loop will tend to …….

1. moves towards positive x-direction

2. moves towards negative x-direction

3. expand

4. contract

Q. Magnetic field due to a current carrying toroidal at the inside of toroid is independent on

1. number of turns of toroid
2. current passes through it
3. mean radius of toroid
4. All of the above

Q. A conducting rod AC of length $4l$ is rotated about a point O in a uniform magnetic field directed into the paper. AO $=l$ and OC $=3l$. Then

1. $V_A-V_O=\frac{B\omega l^2}{2}$
2. $V_O-V_C=\frac{9}{2}B\omega l^2$
3. $V_A-V_C=4B\omega l^2$
4. $V_C-V_O=\frac{9}{2}B\omega l^2$

Q. Consider the charge configuration and a spherical gaussian surface as shown in the figure. When calculating the flux of the electric field through the spherical surface, the electric field will be due to

1. $+q_2$
2. only the positive charges.
3. all the charges in the system
4. $+q_1$ and $-q_1$

Q.

Define the term magnetic field. How it is represented graphically?