List of top Physics Questions on Electromagnetic Field (EMF) asked in JEE Main

Force on a charge \( q = 10^{-9} \, \text{C} \) in uniform electric and magnetic fields is \( \vec{F} = (2 \times 10^{-10} \hat{i} + 3 \times 10^{-10} \hat{j}) \, \text{N} \).

Find the velocity (in m/s) of the charge if the electric field is \( 0.4 \hat{j} \, \text{V/m} \) and the magnetic field is \( 2 \times 10^{-3} \hat{k} \, \text{T} \).

In the first configuration (1) as shown in the figure, four identical charges \( q_0 \) are kept at the corners A, B, C and D of square of side length \( a \). In the second configuration (2), the same charges are shifted to mid points C, E, H, and F of the square. If \( K = \frac{1}{4\pi \epsilon_0} \), the difference between the potential energies of configuration (2) and (1) is given by:

 In the first configuration (1) as shown in the figure, four identical charges \( q_0 \) are kept at the corners A, B, C and D of square of side length \( a \). In the second configuration (2), the same charges are shifted to mid points C, E, H, and F of the square. If \( K = \frac{1}{4\pi \epsilon_0} \), the difference between the potential energies of configuration (2) and (1) is given by:

The fractional compression \( \frac{\Delta V}{V} \) of water at the depth of 2.5 km below the sea level is:
A solenoid having area $ A $ and length $ \ell $ is filled with a material having relative permeability 2. The magnetic energy stored in the solenoid is:

A proton is moving undeflected in a region of crossed electric and magnetic fields at a constant speed of \( 2 \times 10^5 \, \text{m/s} \). When the electric field is switched off, the proton moves along a circular path of radius 2 cm. The magnitude of electric field is \( x \times 10^4 \, \text{N/C} \). The value of \( x \) is \(\_\_\_\_\_\). (Take the mass of the proton as \( 1.6 \times 10^{-27} \, \text{kg} \)).

Due to presence of an em-wave whose electric component is given by \( E = 100 \sin(\omega t - kx) \, NC^{-1} \), a cylinder of length 200 cm holds certain amount of em-energy inside it. If another cylinder of same length but half diameter than previous one holds same amount of em-energy, the magnitude of the electric field of the corresponding em-wave should be modified as:

Due to the presence of an em-wave whose electric component is given by \( E = 100 \sin(\omega t - kx) \, \text{N/C} \), a cylinder of length 200 cm holds a certain amount of em-energy inside it. If another cylinder of the same length but half the diameter of the previous one holds the same amount of em-energy, the magnitude of the electric field of the corresponding em-wave should be modified as:
A square loop of side 15 cm being moved towards right at a constant speed of 2 cm/s as shown in figure. The front edge enters the 50 cm wide magnetic field at t = 0. The value of induced emf in the loop at t = 10 s will be :
An emf of 0.08 V is induced in a metal rod of length 10 cm held normal to a uniform magnetic field of 0.4 T, when moves with a velocity of:

In a potentiometer arrangement, a cell gives a balancing point at 75 cm length of wire. This cell is now replaced by another cell of unknown emf. If the ratio of the emf’s of two cells respectively is 3 : 2, the difference in the balancing length of the potentiometer wire in above two cases will be _____ cm.

A metallic rod of length 4 m is rotating about perpendicular bisector of the rod with angular velocity of 2 rad/s in presence of transverse magnetic field of 0.5 T. Potential difference developed across ends of rod is
An electromagnetic radiation of intensity 360 W /cm2 is incident normally on a non-reflecting surface having area A. Average force on the surface is found to be 2.4 x 10-4 N. Find the value of A.