Current Electricity — Physics STD 12 Science — Question

Answer the following questions.

1. Write SI unit of electric field intensity.
2. Write SI unit of electric dipole moment.

An electric bulb is hanging over a table at a height of 1m above it. The illuminance on the table directly below the bulb is 40 lux. The illuminance at a point on the table 1m away from the first point will be about:

1. 10 lux
2. 14 lux
3. 20 lux
4. 28 lux

Is the ratio of frequencies of ultraviolet rays and infrared rays in glass more than, less than or equal to 1?

Name two semiconductor materials.

What is the basic reason of refraction?

What is the relationship between the radius R of a nucleus and the mass number (A) of an atom?

A light ray is incident perpendicularly on a plane mirror. What will be the values of angle of incidence and angle of reflection?

1kg of ice at 0°C is mixed with 1kg of steam at 100°C. What will be the composition of the system when thermal equilibrium is reached? Latent heat of fusion of ice = 3.36 × 10³ J kg^-1 and latent heat of vaporization of water = 2.26 × 10⁶ J kg^-1.

A cube of iron (density = 8000kg m^-3, specific heat capacity = 470J kg^-1 K^-1) is heated to a high temperature and is placed on a large block of ice at 0°C. The cube melts the ice below it, displaces the water and sinks. In the final equilibrium position, its upper surface just goes inside the ice. Calculate the initial temperature of the cube. Neglect any loss of heat outside the ice and the cube. The density of ice = 900kg m^-3 and the latent heat of fusion of ice = 3.36 × 10⁵J kg^-1.

Two wires of equal length are bent in the form of two loops. One of the loops is square shaped whereas the other loop is circular. These are suspended in a uniform magnetic field and the same current is passed through them. Which loop will experience greater torque? Give reasons.