Assertion (A) Television signals are received through sky-wave propagation.Reason (R) The ionosphere reflects electromagnetic waves of frequencies in the range ( 3- 30) \(\mathrm{MHz}\). Choose the correct option.

In \(p-n-p\) transistor, the collector current is

Statement (I) : A uniform electric field and a uniform magnetic field are pointed in the same direction. If an electron is projected in the same direction the electron velocity will decrease in magnitude. Statement (II) : Two infinite long parallel wires are carrying current in the same direction. The magnetic field at a point midway between the wires is zero. Statement (III) : No net force acts on a rectangular coil carrying a steady current when suspended in a uniform magnetic field. Which of the following is correct?

Four resistors \(A, B, C\) and \(D\) form a Wheatstones bridge. The bridge is balanced, when \(C=100 \Omega\). If \(A\) and \(B\) are interchanged, the bridge balances for \(C=121 \Omega\). The value of \(D\) is

A wheel undergoes a constant angular acceleration from time $t=0$ to $t=20 \mathrm{s}$ and thereafter angular acceleration is zero. If angular velocity at $t=2 \mathrm{s}$ is found to be $5 \mathrm{rad}/\mathrm{s},$ then the number of revolutions made by the wheel in time interval $t=0 \mathrm{s}$ to $t=50 \mathrm{s}$ is

A body cools from a temperature of \(60^{\circ} \mathrm{C}\) to \(50^{\circ} \mathrm{C}\) in 10 minutes and \(50^{\circ} \mathrm{C}\) to \(40^{\circ} \mathrm{C}\) in 15 minutes. The time taken in minutes for the body to cool from \(40^{\circ} \mathrm{C}\) to \(30^{\circ} \mathrm{C}\) is

A vessel contains hydrogen and nitrogen gases in the ratio \(2: 3\) by mass. If the temperature of the mixture of the gases is \(30^{\circ} \mathrm{C}\), then the ratio of the average kinetic energies per molecule of hydrogen and nitrogen gases is (Molecular mass of hydrogen gas \(=2\) and molecular mass of nitrogen gas \(=28\))

Consider a wire of length \(L\) with a resistance of \(5 \Omega\). Applying an external force, the wire is elongated such that its length becomes \(3 L\). Assuming, the resistivity and density of the material is unchanged, the resistance of the elongated wire is

The pressure to be applied to the ends of a steel cylinder to keep its length constant upon raising its temperature by \(100^{\circ} \mathrm{C}\) is (thermal expansion coefficient, \(\alpha=11 \times 10^{-6} / \mathrm{K}\), Young's modulus \(=200 \mathrm{GPa}\) )

Statement (I) : The slope of kinetic energy-displacement curve of a body in motion will be directly proportional to its acceleration. Statement (II) : From a height of \(15 \mathrm{~m}\) a ball is projected vertically upwards with a velocity of \(30 \mathrm{~m} / \mathrm{s}\). If the ball rises to the same height after hitting the ground, the loss of its energy on hitting the ground is \(30 \%\). Statement (III) : The velocity acquired by a body of mass ' \(m\) ' after travelling a fixed distance from rest under the action of a constant force is directly proportional to mass ' \(\mathrm{m}\) '. Which of the following is correct?

On a particular day, the sun delivers an average power of \(\left(\frac{6}{\pi} \times 10^3\right) \frac{\mathrm{W}}{\mathrm{m}^2}\) to the top of Earth's atmosphere. Find the amplitude of magnetic field for the electromagnetic waves above atmosphere. (Take \(\mu_0=4 \pi \times 10^{-7}\) SI unit)

A ball thrown upwards vertically reaches a height \(25 \mathrm{~m}\) in \(1 \mathrm{~s}\). The ratio of total distance covered by the ball in time \(t=2 \mathrm{~s}\) and \(t=4 \mathrm{~s}\) is (Use, \(g=10 \mathrm{~m} / \mathrm{s}^2\) )

For a television network, \(5 \times 10^5\) channels are granted. If the central frequency of the microwave link is \(25 \mathrm{GHz}\) and the alloted bandwidth for each channel is \(2 \mathrm{kHz}\), then how much percentage of the link is used for the network?