Electricity — Science STD 10 — Question

Which among the following is the commercial unit of electrical energy:

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.

An object is placed 20cm in front of a plane mirror. The mirror is moved 2cm towards the object. The distance between the positions of the positions of the original and final images seen in the mirror is:

1. 2cm.
2. 4cm.
3. 10cm.
4. 22cm

A magnetic field is produced by the current passing through a long straight wire. When will the strength of the magnetic field increase?

A spherical mirror to be made from a cut portion of:

Refraction of light in the eye occurs at:

The red colour of the sun at the time of sunrise and sunset is because:

1. Red colour is least scattered.
2. Blue colour is least scattered.
3. Red colour is most scattered.
4. Blue colour is most scattered.

A child is standing in front of a magic mirror. She finds the image of her head bigger, the middle portion of her body of the same size and that of the legs smaller. The following is the order of combinations for the magic mirror from the top.

1. Plane, convex and concave.
2. Convex, concave and plane.
3. Concave, plane and convex.
4. Convex, plane and concave.

Which device uses slip rings?