Electromagnetic Waves — Physics STD 12 Science — Question

The 'rad' is the correct unit used to report the measurement of:

A strip of copper and another of germanium are cooled from room temperature to 80 K. The resistance of

(a) Each of these increases

(b) Each of these decreases

(c) Copper strip increases and that of germanium decreases

(d) Copper strip decreases and that of germanium increases

When a drop of oil is spread on a water surface, it displays beautiful colours in daylight because of:

A charged particle is free to move in an electric field. It will travel:

A charge q is located at the centre of a cube. The electric flux through any face is

(a)

(b)

(c)

(d)

A wall clock uses a vertical spring-mass system to measure the time. Each time the mass reaches an extreme position, the clock advances by a second. The clock gives correct time at the equator. If the clock is taken to the poles it will:

1. Run slow.
2. Run fast.
3. Stop working.
4. Give correct time.

The mass number of a nucleus is equal to the number of

(a) Electrons it contains	(b) Protons it contains
(c) Neutrons it contains	(d) Nucleons it contains

An electric bulb illuminates a plane surface. The intensity of illumination on the surface at a point 2m away from the bulb is 5  phot (lumen/cm²). The line joining the bulb to the point makes an angle of 60^o with the normal to the surface. The intensity of the bulb in candela is

(a) 40

(b) 40

(c) 20

(d) 40

The V-i graph for a conductor makes an angle θ with V-axis. Here V denotes the voltage and i denotes current. The resistance of conductor is given by

(a) sin θ

(b) cos θ

(c) tan θ

(d) cot θ