Physics Test - 3

An electric dipole of dipole moment p is placed in uniform electric field of strength E. If θ is the angle between p and E, then potential energy of the dipole becomes maximum, when θ is

A straight wire of diameter 0.5 mm carrying a current of 1 A is replaced by another wire of 1 mm diameter carrying the same current. The magnetic field far away will be

The reason for the continuous emission of energy by the sun is

A radioactive element has a half life of 15 years. The fraction that will decay in 30 years is

The photoelectric threshold of a certain metal is 30 Å. If the radiation of 2000 Å is incident on the metal

A double convex lens made of air with both radii of curvature being 10 cm is placed in a medium of refractive index 1.5. The focal length and nature of lens is

In comparison to a half wave rectifier, the full wave rectifier gives lower

If a full wave rectifier circuit is operating from 50 Hz mains, then fundamental frequency in the ripple will be

The current gain for a transistor working as common-base amplifier is 0.96. If the emitter current is 7.2 mA, then the base current is

To obtain electrons as majority charge carriers in a semiconductor, the impurity mixed is