Silicon can be doped to get an n-type semiconductor by using :
(A) Arsenic (As),
(B) Phosphorus (P),
(C) Boron (B),
(D) Antimony (Sb).

A long solenoid carrying a current produces a magnetic field B along its axis. If the value of current is halved and the number of turns per unit length is doubled then the new value of magnetic field is:

The equipotential surfaces due to an isolated point charge \( q < 0 \) are:

For a coil of 5 turns, the magnetic flux varies with time as \( \phi_{B}(t) = (2t^3 - \frac{5}{2}t^2 + t) \), where \( \phi_{B}(t) \) and t are in S.I. units. The induced current at t = 2 s in the coil, if its total resistance is 150 \( \Omega \), is :

The shortest wavelength of the spectral lines emitted in Balmer Series is : [Rydberg constant \( = 10^7 \text{ m}^{-1} \)]

A short bar magnet placed with its axis at \(30^\circ\) with a uniform external magnetic field of 0.24 T experiences a torque of magnitude 0.048 N m. The magnetic moment of the magnet is

'n' identical small drops are charged to V volt each. They coalesce to form a bigger drop. The potential of the bigger drop will be:

Maximize \(z=2 x-y\)
Subject to constraints
\(x+y \leq 4, \quad x+3 y \leq 6, \quad x \geq 0, \quad y \geq 0 .\)
The corner points of the feasible region are:

There are two thin parallel charged sheets having surface charge density \( \sigma \) placed at a small distance apart. Which of the following statements are correct?
(A) If both the sheets are positively charged, then the electric field between them is \( \sigma/\epsilon_0 \)
(B) If both the sheets are negatively charged, then the electric field between them is \( \sigma/\epsilon_0 \)
(C) If the left sheet is positively charged and the right sheet is negatively charged the field between them is \( \sigma/\epsilon_0 \)
(D) If the right sheet is positively charged and the left sheet is negatively charged then the field between them is \( \sigma/\epsilon_0 \)
Choose the correct answer from the options given below:

A charge of magnitude \( 3 \times 10^{-7} \, C \) is located at a distance of 0.09 m from a point P. Obtain the work done in bringing a charge of \( 2 \times 10^{-9} \, C \) from infinity to the point P.

The symptoms of Elephantiasis :
(A) Inflammation of lower limb
(B) Scaly lesions on scalp
(C) Anaemia and blockage of intestinal passage
(D) Gross deformities of genital organs
Choose the correct answer from the options given below :

Which of the following techniques are used for early molecular diagnosis of disease?
(A) Urine analysis
(B) PCR
(C) ELISA
(D) RDT
Choose the correct answer from the options given below:

You are given three magnetic needles \( N_F, N_P \) and \( N_D \) made up of ferromagnetic, paramagnetic and diamagnetic materials respectively. If a magnet is brought close to each of the needle one by one, then the magnet will :