Ray Optics and Optical Instruments — Physics STD 12 Science — Question

Two identical heaters rated 220 volt, 1000 watt are placed in series with each other across 220 volt lines. If resistance do not change with temperature, then the combined power is

(a) 1000 watt

(b) 2000 watt

(c) 500 watt

(d) 4000 watt

The potential difference in open circuit for a cell is 2.2 volts. When a 4 ohm resistor is connected between its two electrodes the potential difference becomes 2 volts. The internal resistance of the cell will be

(a) 1 ohm

(b) 0.2 ohm

(c) 2.5 ohm

(d) 0.4 ohm

Which of the following is not a unit of magnetic induction?

In an inelastic collision:

1. The initial kinetic energy is equal to the final kinetic energy.
2. The final kinetic energy is less than the initial kinetic energy.
3. The kinetic energy remains constant.
4. The kinetic energy first increases then decreases.

In a charged capacitor, the energy is stored in:

Two identical magnetic dipoles of magnetic moments 1.0 A-m² each, placed at a separation of 2m with their axis perpendicular to each other. The resultant magnetic field at a point midway between the dipoles is

(a) 5

(b)

(c)

(d) None of these

Resistance of capacitor for high frequency is:

Electron-volt (eV) is the measure of:

The counting rate observed from a radioactive source at t = 0 second was 1600 counts per second and at t = 8 seconds it was 100 counts per second. The counting rate observed, as counts per second at t = 6 seconds, will be

(a) 400

(b) 300

(c) 200

(d) 150

Which color band in the resistor is having highest tolerance?