Electromagnetism PYQ — Page 2

The value of electric potential at a distance of 9 cm from the point charge $4 \times 10^{-7} \mathrm{C}$ is $\left[\right.$ Given $\left.\frac{1}{4 \pi \varepsilon_0}=9 \times 10^9 \mathrm{~N} \mathrm{~m}^2 \mathrm{C}^{-2}\right]$ :

The capacitance of a capacitor with charge $q$ and a potential difference $V$ depends on

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 

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:

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:

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

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.

A uniform wire of diameter $d$ carries a current of 100 mA when the mean drift velocity of electrons in the wire is $v$. For a wire of diameter $\frac{d}{2}$ of the same material to carry a current of 200 mA , the mean drift velocity of electrons in the wire is

The terminal voltage of the battery, whose emf is 10 V and internal resistance $1 \Omega$, when connected through an external resistance of $4 \Omega$ as shown in the figure is: 

 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 step up transformer is connected to an ac mains supply of 220 V to operate at $11000 \mathrm{~V}, 88$ watt. The current in the secondary circuit, ignoring the power loss in the transformer, is

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 $(\pi=3.14)$ : 

A wire of length ' 1 and resistance $100 \Omega$ is divided into 10 equal parts. The first 5 parts are connected in series while the next 5 parts are connected in parallel. The two combinations are again connected in series. The resistance of this final combination is:

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:

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

In an ideal transformer, the turns ratio is $\frac{N_P}{N_S}=\frac{1}{2}$. The ratio $V_S: V_P$ is equal to (the symbols carry their usual meaning) :

If the ratio of relative permeability and relative permittivity of a uniform medium is $1: 4$. The ratio of the magnitudes of electric field intensity $(E)$ to the magnetic field intensity $(H)$ of an EM wave propagating in that medium is (Given that $\sqrt{\frac{\mu_0}{\varepsilon_0}}=120 \pi$ )

The electromagnetic radiation which has the smallest wavelength are

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

A metal cube of side 5 cm is charged with $6 \mu \mathrm{C}$. The surface charge density on the cube is

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: