Electromagnetism PYQ — Page 12

In a region the potential is represented by $V(x, y, z)=6x-8xy-8y+6yz,$ where $V$ is in volts and $x, y, z,$ are in meters. The electric force experienced by a charge of $2$ coulombs situated at point $(1, 1, 1)$ is:

Two identical long conducting wires $AOB$ and $COD$ are placed at right angle to each other, with one above other such that ‘ $O$ ’ is their common point for the two. The wires carry ${I}_{1}$ and ${I}_{2}$ currents, respectively. Point ‘ $I$ ’ is lying at distance ‘ $d$ ’ from ‘ $O$ ’ along a direction perpendicular to the plane containing the wires. The magnetic field at the point ‘ $P$ ’ will be:

Light with an energy flux of $25\times {10}^{4} {Wm}^{-2}$ falls on a perfectly reflecting surface at normal incidence. If the surface area is $15 {cm}^{2},$ the average force exerted on the surface is:

Two thin dielectric slabs of dielectric constants ${K}_{1}$ and ${K}_{2}({K}_{1}<{K}_{2})$ are inserted between plates of a parallel plate capacitor, as shown in the figure. The variation of electric field ‘ $E$ ’ between the plates with distance ‘ $d$ ’ as measured from plate $P$ is correctly shown by: 

Following figures show the arrangement of bar magnets in different configurations. Each magnet has magnetic dipole $\vec{m}.$ Which configuration has highest net magnetic dipole moment?

A conducting sphere of radius $R$ is given a charge $Q.$ The electric potential and the electric field at the center of the sphere respectively are:

In an ammeter $0.2%$ of main current passes through the galvanometer. If resistance of galvanometer is $G,$ the resistance of ammeter will be:

A bar magnet of magnetic moment $M$ placed at right angles to a magnetic induction $B$. If a force $F$ is experienced by each pole of the magnet. The length of the magnet will be:

Two rods are joined to end, as shown. Both have a cross sectional area of 0.01 $\mathrm{cm}^2$. Each is 1 meter long. One rod is of copper with a resistivity of $17 \times 10^{-6}$ ohm-centimeter, the other is of iron with a resistivity of $10^{-5} \mathrm{ohm}$ centimeter. How much voltage is required to produce a current of 1 ampere in the rods? 

A coil of self-inductance $L$ is connected in series with a bulb $B$ and an $A C$ source. Brightness of the bulb decreases when

An electromagnetic wave of frequency $v=3.0 \mathrm{MHz}$ passes from vacuum into a dielectric medium with relative permittivity $\varepsilon=4.0$ Then:

$A, B$ and $C$ are three points in a uniform electric field. The electric potential is 

A bar magnet of length $l$ and magnetic dipole moment $M$ is bent in the form of an arc as shown in figure. The new magnetic dipole moment will be 

A wire of resistance $4 \Omega$ is stretched to twice its original length. The resistance of stretched wire would be

The primary winding of transformer when connected to a $d c$ battery of 10 Volt draws a current of $1 \mathrm{~mA}$. The number of turns of the primary and secondary windings are 50 and 100 respectively. The voltage in the secondary and the current drawn by the circuit in the secondary are respectively:

Ten identical cells connected in series are needed to heat a wire of length one meter and radius ' $r$ ' by $10^{\circ} \mathrm{C}$ in time ' $t$ '. How many cells will be required to heat the wirc of length two meter of the same radius by the same temperature in time 'r'?

A current of $2.5 \mathrm{~A}$ flows through a coil of inductance $5 \mathrm{H}$. The magnetic flux linked with the coil is:

The resistances of the four arms $P, Q, R$ and $S$ in a Wheatstone's bridge are $10 \Omega, 30 \Omega, 30 \Omega$ and $90 \Omega$, respectively. The emf and internal resistance of the cell are $7 \mathrm{~V}$ and $5 \Omega$ respectively. If the galvanometer resistance is $50 \Omega$, the current drawn from the cell will be

A long straight wire carries a certain current and produces a magnetic field $2 \times 10^{-4} \frac{\text { Weber }}{\mathrm{m}^2}$ at a perpendicular distance of $5 \mathrm{~cm}$ from the wire. An electron situated at $5 \mathrm{~cm}$ from the wire moves with a velocity $10^7 \mathrm{~m} / \mathrm{s}$ towards the wire along perpendicular to it. The force experienced by the electron will be (change on electron $1.6 \times 10^{-19} \mathrm{C}$ )

Two pith balls carrying equal charges are suspended from a common point by strings of equal length, the equilibrium separation between them is $r$. Now the strings are rigidly clamped at half the height. The equilibrium separation between the balls now become. 

A circular $A B C D$ carrying a current ' $i$ ' is placed in a uniform magnetic field, if the magnetic force on the segment $A B$ is $\vec{F}$, the force on the remaining segment BCDA is: 

An electric dipole of dipole moment $p$ is aligned parallel to a uniform electric field $E$. The energy required to rotate the dipole by $90^{\circ}$ is:

The condition under which a microwave oven heats up a food item containing water molecules most efficiently is

The internal resistance of a $2.1 \mathrm{~V}$ cell which gives a current of $0.2 \mathrm{~A}$ through a resistance of $10 \Omega$ is