A piece of copper and a piece of germanium are cooled from room temperature 20 C down to 80 K. The resistance of

Two parallel plate capacitors, X and Y, have the same area of plates and the same separation between them. They are connected in series across a 12 V battery. X has air between the plates while Y contains a dielectric medium of dielectric constant 4. The ratio of electrostatic energy stored in X and Y is

An electron having charge \( 1.6 \times 10^{-19} \text{ C} \) and mass \( 9 \times 10^{-31} \text{ kg} \) is moving with \( 4 \times 10^6 \text{ m/s} \) speed in a magnetic field \( 2 \times 10^{-1} \text{ T} \) in a circular orbit. The force experienced by the electron and the radius of the circular orbit, respectively will be:

The intensity of a plane monochromatic wave is \( 1380 \text{ Wm}^{-2} \). What is the amplitude of electric field in this wave ? (Take speed of light \( 3 \times 10^{8} \text{ ms}^{-1} \); \( \epsilon_{0} = 8.85 \times 10^{-12} \text{ C}^{2}\text{N}^{-1}\text{m}^{-2} \))

If the potential difference across a capacitor is changed from 12 V to 24 V, the work done is W. How much work will be done if the potential difference is changed from 24 V to 48 V?

A proton, a deuteron and an alpha particle have the same kinetic energy and move in a uniform magnetic field perpendicular to their direction of motion. The ratio of the radii of their circular paths is :

The power factor of an ac circuit having resistance \( R \) and inductance \( L \) connected in series is :

igure given below shows variation of photocurrent with anode potential for different intensities of incident radiation. Some of the results obtained from the experiments are described below on the basis of the graph. Identify the correct results:

(A) The photoelectric current is higher for higher intensity of the incident radiation.
(B) The negative potential required to decrease the photocurrent at different intensities to zero is different.
(C) If the positive potential of the anode is increased beyond a certain value, the photocurrent does not increase for a given intensity.
(D) If the potential applied at the anode is zero, then the photocurrent is lower than the maximum value of current for the given intensity.
Choose the correct answer from the options given below:

Aphids and mosquitoes can be controlled by, respectively:

Arrange the given organisms involved in an ecosystem in correct sequence from lower to higher order.
(A) Fish
(B) Phytoplankton
(C) Man
(D) Zooplankton
Choose the correct answer from the options given below:

The probability distribution of number of heads in two tosses of a coin is:

Arrange the following in the increasing order of de-Broglie wavelength:
A. A bullet of mass 0.02 kg travelling at speed of 3.3 km s⁻¹
B. A ball of mass 0.0331 kg moving with speed of 2 m s⁻¹
C. A dust particle of mass \( 2 \times 10^{-10} \text{ kg} \) drifting with a speed of 3.3 m s⁻¹
D. A photon having a momentum of \( 6.63 \times 10^{-26} \text{ kg m s}^{-1} \)
E. An electron accelerated through a potential difference of 100 V
Choose the correct answer from the options given below:

In an AC generator, a 100 turns coil of area \(0.10 \text{ m}^2\) rotates at 50 Hz in a uniform magnetic field of 0.01 T. The maximum voltage generated in the coil is