Electricity — Science STD 10 — Question

To obtain a magnification of, -0.5 with a convex lens, the object should be placed:

1. At F
2. Between optical centre and F.
3. Between F and 2F.
4. Beyond 2F.

Electricians wear rubber gloves because:

The medical condition in which the lens of the eye of a person becomes progressively cloudy resulting in blurred vision is called:

Two big mirrors A and B are fitted side by side on a wall. A man is standing at such a distance from the wall that he can see the erect image of his face in both the mirrors. When the man starts walking towards the mirrors, he find that the size of his face in mirror A goes on increasing but that in mirror B remains the same.

1. Mirror A is concave and mirror B is convex.
2. Mirror A is plane and mirror B is concave.
3. Mirror A is concave and mirror B is plane.
4. Mirror A is convex and mirror B is concave.

Following is true for Hypermetropia:

The stars twinkle but the planets do not twinkle at night because:

1. The stars are small but the planets are large.
2. The stars are very large but planets are small.
3. The stars are much nearer but planets are far off.
4. The stars are far off but planets are nearer to earth.

Magnification produced by a concave lens is always:

1. More than 1.
2. Equal to 1.
3. Less than 1.
4. More than 1 or less than 1.

The device used for measuring potential difference is known as:

At a hydro power plant:

1. Kinetic energy possessed by stored water is converted into electrical energy.
2. Electrical is extracted from water.
3. Water is converted into steam to turn turbines and produce electricity.
4. Potential energy possessed by stored water is converted into electricity.