Ferromagnetic material in transformers should have :

Light with an energy flux of \( 18 \text{ W/cm}^2 \) falls at normal incidence on a non-reflecting surface of area \( 20 \text{ cm}^2 \). If the light falls for 30 minutes on the surface, find the total momentum delivered to the surface.

Read the following statements regarding energy levels, and identify the correct statements.
(A) The energy of an atom is least when its electron is revolving in an orbit closest to the nucleus
(B) the energy levels of the excited states come closer and closer together as principal quantum number increases
(C) ionisation energy of the hydrogen atom is the minimum energy required to free the electron from the ground state of the hydrogen atom
(D) as the excitation of hydrogen atom increases, the value of minimum energy required to free the electron from the excited atom decreases.
Choose the correct answer from the options given below:

The half-lives of two radioactive specimens are \(T_1=5\) years and \(T_2=7.5\) years.
The ratio of their disintegration constants \(\lambda_1\) and \(\lambda_2\) is:

The magnetic susceptibility of the material of a rod is 499. Permeability of vacuum is \( 4\pi \times 10^{-7} \text{ H/m} \). The absolute permeability of the material of the rod is:

A resistor, a capacitor and an inductor are joined in series with an alternating current source. If the frequency of the source is slightly increased from a very low value, then :

Identify the basic features of the photon picture of electromagnetic radiation from the following:
(A) Each photon has energy \(E = h\nu\) in vacuum.
(B) Photons are electrically neutral and are not deflected by electric and magnetic fields.
(C) All photons of light of a particular frequency \(\nu\) or wavelength \(\lambda\) have the same energy and momentum.
(D) If the intensity of light of a given wavelength is increased, there is an increase in the number of photons incident on a given area in a given time.
Choose the correct answer from the options given below:

The conductivity of electrolytic solutions does not depend upon

A spherical conductor placed in vacuum has capacitance of \( 3.14 \times 10^{-9} \, \text{F} \). Its radius will be:

If the points P, Q, R with position vectors \(5 \hat{i}+\lambda \hat{j}, 20 \hat{i}-\hat{j}\) and \(15 \hat{i}- 6\hat{j}\) respectively are colinear, then the value of \(\lambda\) is

If \(\left[\begin{array}{ccc}x-2 & 3 & -2 \\ y & 0 & -4 \\ 2 & z & 0\end{array}\right]\) is a skew symmetric matrix, then the value of \(x+y+z\) is

Maximum value of the objective function Z = 4x + 3y subject to the constraints \(x+y \geq 4, x \geq 4, y \geq 0\) exists at

Let \(A\) be any square matrix of order 3 and \(B=\left[\begin{array}{ccc}0 & -4 & 2 \\ 4 & 0 & 3 \\ -2 & -3 & 0\end{array}\right]\).Then the matrix \(A B A^T\) is a: