Current Electricity — Physics STD 12 Science — Question

A thin metal plate P is inserted between the plates of a parallel-plate capacitor of capacitance C in such a way that its edges touch the two plates (figure). The capacitance now becomes:

The most commonly used material for making transistor is

(a) Copper

(b) Silicon

(c) Ebonite

(d) Silver

An ice cube is suspended in vacuum in a gravity free hall. As the ice melts it.

1. Will retain its cubical shape.
2. Will change its shape to spherical.
3. Will fall down on the floor of the hall.
4. Will fly up.

In a large building, there are 15 bulbs of 40W, 5 bulbs of 100W, 5 fans of 80W and 1 heater of 1kW. The voltage of electric mains is 220V. The minimum capacity of the main fuse of the building will be:

The fundamental frequency of a string is proportional to:

1. Inverse of its length.
2. The diameter.
3. The tension.
4. The density.

Substances in which the magnetic moment of a single atom is not zero, is known as

(a) Diamagnetism

(b) Ferromagnetism

(c) Paramagnetism

(d) Ferrimagnetism

Fusion reaction is initiated with the help of

(a) Low temperature

(b) High temperature

(c) Neutrons

(d) Any particle

To an observer on the earth the stars appear to twinkle. This can be ascribed to

(a) The fact that stars do not emit light continuously

(b) Frequent absorption of star light by their own atmosphere

(c) Frequent absorption of star light by the earth's atmosphere

(d) The refractive index fluctuations in the earth's atmosphere

When a resistance of 2ohm is connected across the terminals of a cell, the current is 0.5 amperes. When the resistance is increased to 5 ohm, the current is 0.25 amperes. The internal resistance of the cell is

(a) 0.5 ohm

(b) 1.0 ohm

(c) 1.5 ohm

(d) 2.0 ohm

What is the space around a current-carrying conductor, in which its magnetic effect can be experienced called?