Magnetic Effects of Electric Current — Science STD 10 — Question

The mirror used by a dentist to examine the teeth of a person is:

A virtual image three times the size of the object is obtained with a concave mirror of radius of curvature 36cm. The distance of the object from the mirror is:

A hollow glass prism gives:

A car headlight bulb working on a 12V car battery draws a current of 0.5A. The resistance of the light bulb is:

An object is placed in front of a screen and a convex lens is placed at a position such that the size of the image formed is 9cm. when the lens is shifted through a distance of 20cm, the size of the image becomes 1cm. The focal length of the lens and the size of the object are respectively.

One type of energy which has not been controlled so far is:

1. Ocean thermal energy.
2. Nuclear fusion energy.
3. Geothermal energy.
4. Nuclear fission energy.

The refractive indices of four media A, B, C and D are 1.44, 1.52, 1.65 and 1.36 respectively. When light travelling in air is incident in these media at equal angles, the angle of refraction will be the minimum:

In the concave reflector of a torch, the bulb is placed:

1. Between the pole and focus of reflector.
2. At the focus of reflector.
3. Between focus and centre of curvature of reflector.
4. At the centre of curvature of reflector.

Which of the following changes occur when you walk out of bright sunshine into a poorly lit room?

1. The pupil becomes larger.
2. The lens becomes thicker.
3. The ciliary muscle relaxes.
4. The pupil becomes smaller.

A student carries out an experiment and plots the V-I graph of three samples of nichrome wire with resistances R₁, R₂ and R₃ respectively (Figure). Which of the following is true?

1. R₁ = R₂ = R₃
2. R₁ > R₂ > R₃
3. R₃ > R₂ > R₁
4. R₂ > R₃ > R₁