Electromagnetism PYQ — Page 2

The magnetic moment and moment of inertia of a magnetic needle as shown are, respectively, $1.0 \times 10^{-2} \mathrm{~A} \mathrm{~m}$ and $\frac{10^{-6}}{\pi^2} \mathrm{~kg} \mathrm{~m}^2$. If it completes 10 oscillations in 10 s , the magnitude of the magnetic field is 

The electromagnetic radiation which has the smallest wavelength are

If the plates of a parallel plate capacitor connected to a battery are moved close to each other, then A. the charge stored in it, increases. B. the energy stored in it, decreases. C. its capacitance increases. D. the ratio of charge to its potential remains the same. E. the product of charge and voltage increases. Choose the most appropriate answer from the options given below:

In a uniform magnetic field of 0.049 T , a magnetic needle performs 20 complete oscillations in 5 seconds as shown. The moment of inertia of the needle is $9.8 \times 10^{-6} \mathrm{~kg} \mathrm{~m}^2$. If the magnitude of magnetic moment of the needle is $x \times 10^{-5} \mathrm{Am}^2$, then the value of ' $x$ ' is : 

Let us consider two solenoids $A$ and $B$, made from same magnetic material of relative permeability $\mu_r$ and equal area of cross-section. Length of $A$ is twice that of $B$ and the number of turns per unit length in $A$ is half that of $B$. The ratio of self inductances of the two solenoids, $L_A: L_B$ is

A thin spherical shell is charged by some source. The potential difference between the two points $C$ and $P$ (in V ) shown in the figure is: (Take $\frac{1}{4 \pi \varepsilon_0}=9 \times 10^9$ SI units) 

Given below are two statements: One is labelled as Assertion A and the other is labelled as Reason R. Assertion A: Houses made of concrete roofs overlaid with foam keep the room hotter during summer. Reason R: The layer of foam insulation prohibits heat transfer, as it contains air pockets. In the light of the above statements, choose the correct answer from the options given below.

 In the above diagram, a strong bar magnet is moving towards solenoid-2 from solenoid-1. The direction of induced current in solenoid-1 and that in solenoid-2, respectively, are through the directions:

A $10 \mu \mathrm{F}$ capacitor is connected to a $210 \mathrm{~V}, 50 \mathrm{~Hz}$ source as shown in figure. The peak current in the circuit is nearly $(\pi=3.14)$ : 

Choose the correct circuit which can achieve the bridge balance.

An iron bar of length $L$ has magnetic moment $M$. It is bent at the middle of its length such that the two arms make an angle $60^{\circ}$ with each other. The magnetic moment of this new magnet is :

In an electrical circuit, the voltage is measured as $V=(200 \pm 4)$ volt and the current is measured as $I=(20 \pm 0.2) \mathrm{A}$. The value of the resistance is:

The magnetic potential energy, when a magnetic bar of magnetic moment $\vec{m}$ is placed perpendicular to the magnetic field $\vec{B}$ is

A 12 pF capacitor is connected to a 50 V battery, the electrostatic energy stored in the capacitor in nJ is

A tightly wound 100 turns coil of radius 10 cm carries a current of 7 A . The magnitude of the magnetic field at the centre of the coil is (Take permeability of free space as $4 \pi \times 10^{-7}$ SI units):

Given below are two statements: Statement I : The Indian Government has set up GEAC, which will make decisions regarding the validity of GM research. Statement II : Biopiracy is the term used to refer to the use of bio-resources by native people. In the light of the above statements, choose the correct answer from the options given below

Given below are two statements: one is labelled as Assertion $\mathbf{A}$ and the other is labelled as Reason $\mathbf{R}$. Assertion A: The potential $(V)$ at any axial point, at 2 m distance $(r)$ from the centre of the dipole of dipole moment vector $\vec{P}$ of magnitude, $4 \times 10^{-6} \mathrm{C} \mathrm{m}$, is $\pm 9 \times 10^3 \mathrm{~V}$. (Take $\frac{1}{4 \pi \epsilon_0}=9 \times 10^9$ SI units) Reason $\mathbf{R}$ : $V= \pm \frac{2 P}{4 \pi \epsilon_0 r^2}$, where $r$ is the distance of any axial point, situated at 2 m from the centre of the dipole. In the light of the above statements, choose the correct answer from the options given below:

In the following circuit, the equivalent capacitance between terminal $A$ and terminal $B$ is : 

Match List-I with List-II. $\begin{array}{ll|rl} & \text{List-I} & & \begin{array}{l} \text{List-II} \\ \text{(Susceptibility } (\chi))\end{array} \\ \hline A. & \text{Diamagnetic} & I. & \chi=0 \\ B. & \text{Ferromagnetic} & II. & 0 \gt \chi \geq-1 \\ C. & \text{Paramagnetic} & III. & \chi \gt \gt 1 \\ D. & \text{Non-magnetic} & IV. & 0 \lt \chi \lt \varepsilon \text{(a small positive number)} \end{array}$ Choose the correct answer from the options given below

A sheet is placed on a horizontal surface in front of a strong magnetic pole. A force is needed to: A. hold the sheet there if it is magnetic. B. hold the sheet there if it is non-magnetic. C. move the sheet away from the pole with uniform velocity if it is conducting. D. move the sheet away from the pole with uniform velocity if it is both, non-conducting and non-polar. Choose the correct statement(s) from the options given below:

The given circuit shows a uniform straight wire $A B$ of 40 cm length fixed at both ends. In order to get zero reading in the galvanometer $G$, the free end of $J$ is to be placed from $B$ at: 

The magnetic moment of an iron bar is $M$. It is now bent in such a way that it forms an arc section of a circle subtending an angle of $60^{\circ}$ at the centre. The magnetic moment of this arc section is

A parallel plate capacitor is charged by connecting it to a battery through a resistor. If $I$ is the current in the circuit, then in the gap between the plates:

The steady state current in| the circuit shown below is :