Semiconductor Electronic: Material, Devices And Simple Circuits — Physics STD 12 Science — Question

Can the potential energy in a simple harmonic motion be negative? Will it be so if we choose zero potential energy at some point other than the mean position?

Volt-second is unit of which physical quantity?

A cubical box is to be constructed with iron sheets 1mm in thickness. What can be the minimum value of the external edge so that the cube does not sink in water? Density of iron = 8000kg/m³ and density of water = 1000kg/m³.

With what Hertz produced electro-magnetic waves?

From the following, identify the electromagnetic waves having the:

1. Maximum.
2. Minimum frequency.

1. Radio waves,
2. Gamma-rays,
3. Visible light,
4. Microwaves,
5. Ultraviolet rays,
6. Infrared rays.

Name the electromagnetic waves which :
(a) are useful in removing tension in musceles.
(b) are absorbed by ozone layer in atmosphere.

A fan with copper winding in its motor consumes less power as compared to an otherwise similar fan aluminium winding. Explain.

The value of photoelectric current depend on which factor at constant frequency?

When a forward bias is applied to a p-n junction, it

1. Raises the potential barrier.
2. Reduces the majority carrier current to zero.
3. Lowers the potential barrier.
4. None of the above.

An electric bulb is hanging over a table at a height of 1m above it. The illuminance on the table directly below the bulb is 40 lux. The illuminance at a point on the table 1m away from the first point will be about:

1. 10 lux
2. 14 lux
3. 20 lux
4. 28 lux