Electromagnetism PYQ — Page 21

A bar magnet is oscillating in the Earth's magnetic field with a period $T$. What happens to its period and motion if its mass is quadrupled?

According to Curie's law, the magnetic susceptibility of a substance at an absolute temperature $T$ is proportional to:

An electric kettle has two heating coils. When one of the coils is connected to a.c. source, the water in the kettle boils in 10 minute. When the other coil is used the water boils in 40 minute. If both the coils are connected in parallel, the time taken by the same quantity of water to boil will be:

Fuse wire is a wire of :

A long solenoid carrying a current produces a magnetic field $B$ along its axis. If the current is doubled and the number of turns per $\mathrm{cm}$ is halved, the new value of the magnetic field is:

A charged particle moves through a magnetic field in a direction perpendicular to it. Then the:

An electron is moving around the nucleus of a hydrogen atom in a circular orbit of radius $r$. The coulomb force $\vec{F}$ between the two is: $\left(\right.$ where $\left.K=\frac{1}{4 \pi \varepsilon_0}\right)$

In a Wheatstone's bridge all the four arms have equal resistance $R$. If the resistance of the galvanometer arm is also $R$, the equivalent resistance of the combination as seen by the battery is:

Two 220 volt, 100 watt bulbs are connected first in series and then in parallel. Each time combination is connected to a 220 volt a.c. supply line. The power drawn by the combination in each case respectively will be:

Which of the following rays are not electromagnetic waves?

Which is having a minimum wavelength?

A charge ' $q$ ' moves in a region where the electric field and the magnetic field both exist, then the force on it is:

For a series LCR circuit the power loss at resonance is:

Two bar magnets having geometry with magnetic moments $M$ and $2 M$ are first placed in such a way that their similar poles are same side then its time period of oscillation is $T_1$. Now the polarity of one of the magnet is reversed then the time period of oscillation is $T_2$, so:

The velocity of the electromagnetic wave is parallel to:

A capacitor of capacitance $C_1$ charged up to $V$ volt and then connected to an uncharged capacitor $C_2$. Then, the final potential difference across each will be:

Specific resistance of a conductor increase with:

Some charge is being given to a conductor. Then, its potential:

Identical charges $(-q)$ are placed at each corner of a cube of side ' $b$ ' then the electrical potential energy of charge (+ $q$ ) which is placed at the centre of cube will be:

The magnetic field of a given length of wire for a single turn coil at the centre is ' $B$ ' then, its value for two turns coil for the same wire is:

For a cell, terminal potential difference is $2.2 \mathrm{~V}$ when circuit is open. If it reduces to $1.8 \mathrm{~V}$ when the cell is connected to a resistance of $5 \Omega$. The internal resistance of cell $(r)$ is then:

What is the cause of the 'Greenhouse effect'?

To convert a galvanometer into a voltmeter one should connect a: