Electromagnetism PYQ — Page 11

A radiation of energy $\text{E}$ falls normally on a perfectly reflecting surface. The momentum transferred to the surface is ($\text{C}$ = Velocity of light)

If potential(in $\mathrm{volts}$) in a region is expressed as $V(x,y,z)=6xy-y+2yz$, the electric field(in $N{C}^{-1}$) at point$(1,1,0)$ is

Two metal wires of identical dimensions are connected in series. If ${v}_{1}$ and ${v}_{2}$ are the conductivities of the metal wires respectively, the effective conductivity if the combination is:

Across a metallic conductor of non-uniform cross section a constant potential difference is applied. The quantity which remains constant along the conductor is:

A conducting square frame of side $\text{a}$ and a long straight wire carrying current $\text{I}$ are located in the same plane as shown in the figure. The frame moves to the right with a constant velocity $\text{V}$. The e.m.f induced in the frame (when the centre of the frame is at a distance $x$ from the wire) will be proportional to : 

A potentiometer wire of length $L$ and a resistance $r$ are connected in series with a battery of e.m.f. ${E}_{0}$ and a resistance ${r}_{1}$ . An unknown e.m.f. $E$ is balanced at a length $l$ of the potentiometer wire. The e.m.f. $E$ will be given by:

A potentiometer wire has length $\text{4 m}$ and resistance $8\Omega$ . The resistance that must be connected in series with the wire and an accumulator of e.m.f. $\text{2V}$ , so as to get a potential gradient $\text{1 mV}$ per cm on the wire is :

A wire carrying current $\text{I}$ has the shape as shown in adjoining figure. Linear parts of the wire are very long and parallel to $\text{X}$ -axis while semicircular portion of radius $\text{R}$ is lying in $\text{Y}$ -$\text{Z}$ plane. Magnetic field at point $\text{O}$ is : 

A circuit contains an ammeter, a battery of 30 v and a resistance 40.8 ohm all connected in series. If the ammeter has coil of resistance 480 ohm and a shunt of 20 ohm, the reading in the ammeter will be:

A parallel plate air capacitor of capacitance $C$ is connected to a cell of emf $V$ and then disconnected from it. A dielectric slab of dielectric constant $K$, which can just fill the air gap of the capacitor, is now inserted in it. Which of the following is incorrect?

A parallel plate air capacitor has capacity $\text{C}$, distance of separation between plates is $\text{d}$ and potential difference $\text{V}$ is applied between the plates. The force of attraction between the plates of the capacitor is

A resistance $\text{R}$ draws power $\text{P}$ when connected to an $\text{AC}$ source. If an inductance is now placed in series with the resistance, such that the impedance of the circuit becomes $\text{Z}$ , the power drawn will be:

An electron moving in a circular orbit of radius $r$ makes $n$ rotations per second. The magnetic field produced at the center has magnitude:

A series R-C circuit is connected to an alternating voltage source. Consider two situations: a. When capacitor is air filled. b. When capacitor is mica filled. Current through resistor is $i$ and voltage across capacitor is $V$ then:

$\text{A}$ , $\text{B}$ and $\text{C}$ are voltmeters of resistance $\text{R}$ , $\text{1}\text{.5 R}$ and $\text{3 R}$ respectively as shown in the figure. When some potential difference is applied between $\text{X}$ and $\text{Y}$ , the voltmeter readings are ${V}_{A}, {V}_{B}$ and ${V}_{C}$ respectively. Then: 

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 $0.2$ $Weber/{m}^{2}$ . The coil carries a current of $2\text{A}$. If the plane of the coil is inclined at an angle of ${30}^{o}$ with the direction of the field, the torque required to keep coil in stable equilibrium will be:

The electric field in a certain region is acting radially outward and is given by $E=Ar$. A charge contained in a sphere of radius $\text{a}$ centred at the origin of the field will be given by

An electron moves on a straight line path XY as shown. The abcd is a coil adjacent to the path of electron. What will be the direction of current, if any, induced in the coil? 

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 MeV, the energy acquired by the alpha particle will be:

The resistance in the two arms of the meter bridge are $5 \Omega$ and $R\Omega ,$ respectively. When the resistance $R$ is shunted with an equal resistance, the new balance point is at $1.6{l}_{1}.$ The resistance ‘ $R$ ’ is: 

A transformer having efficiency of $90%$ is working on $200 V$ and $3 kW$ power supply. If the current in the secondary coil is $6 A$ the voltage across the secondary coil and the current in the primary coil respectively are:

Two cities are $150 km$ apart. Electric power is sent from one city to another city through copper wires. The fall of potential per $km$ is $8$ volts and the average resistance per $km$ is $0.5 \Omega .$ The power loss in the wire is:

A potentiometer circuit has been set up for finding the internal resistance of a given cell. The main battery, used across the potentiometer wire, has an emf of $2.0 V$ and a negligible internal resistance. The potentiometer wire itself is $4 m$ long. When the resistance, $R,$ connected across the given cell, has values of. $(i)$ infinity $(ii) 9.5 \Omega$ The 'balancing lengths, on the potentiometer wire are found to be $3m$ and $2.85 m,$ respectively. The value of internal resistance of the cell is:

A thin semicircular conducting ring $(PQR)$ of radius $r$ is falling with its plane vertical in a horizontal magnetic field $B,$ as shown in figure. The potential difference developed across the ring when its speed is $v,$ is: