Electromagnetic Waves — Physics STD 12 Science — Question

In p-type semiconductors, holes are:

The waves used in telecommunication are

(a) IR

(b) UV

(c) Microwave

(d) Cosmic rays

Which of the following gases has maximum rms speed at a given temperature?

1. Hydrogen.
2. Nitrogen.
3. Oxygen.
4. Carbon dioxide.

In a step-up transformer the voltage in the primary is 220 V and the current is 5A. The secondary voltage is found to be 22000V. The current in the secondary (neglect losses) is

(a) 5 A

(b) 50 A

(c) 500 A

(d) 0.05 A

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.

Speed of electromagnetic waves is the same:

1. For all wavelengths.
2. In all media.
3. For all intensities.
4. For all frequencies.

A bar magnet has coercivity 4 .  It is desired to demagnetise it by inserting it inside a solenoid 12 cm long and having 60 turns. The current that should be sent through the solenoid is

(a) 2 A

(b) 4 A

(c) 6 A

(d) 8 A

A Young's double slit experiment uses a monochromatic source. The shape of the interference fringes formed on a screen is

(a) Straight line

(b) Parabola

(c) Hyperbola

(d) Circle

X-rays are in nature similar to

(a) Beta rays

(b) Gamma rays

(c) de-Broglie waves

(d) Cathode rays

A galvanometer whose resistance is  120 Ω gives full scale deflection with a current of 0.05 A so that it can read a maximum current of 10 A. A shunt resistance is added in parallel with it. The resistance of the ammeter so formed is

(a) 0.06 Ω

(b) 0.006 Ω

(c) 0.6 Ω

(d) 6 Ω s