Magnetism and Matter — Physics STD 12 Science — Question

A wave pulse passing on a string with a speed of 40cm/s in the negative x-direction has its maximum at x = 0 at t = 0. Where will this maximum be located at t = 5s?

A photographic plate placed at a distance of 5cm from a weak point source is exposed for 3s. If the plate is kept at a distance of 10cm from the source, the time needed for the same exposure is:

1. 3s
2. 12s
3. 24s
4. 48s

Suppose a charged particle moves with a velocity v near a wire carrying an electric current. A magnetic force, therefore, acts on it. If the same particle is seen from a frame moving with velocity v in the same direction, the charge will be found at rest. Will the magnetic force become zero in this frame? Will the magnetic field become zero in this frame?

A charged particle moving with a uniform velocity enters a magnetic field directed perpendicular to it, what will be the path of electron? How will its speed be affected?

If potential difference across the ends of any conductor in increased from V to 3 V, then how will drift velocity of electron change?

Where on the surface of Earth is the angle of dip 90^o?

Light passes through a closed cylindrical tube containing a gas. If the gas is gradually pumped out, the speed of light inside the tube will:

1. Increase.
2. Decrease.
3. Remain constant.
4. First increase and then decrease.

Give one example of use of eddy currents.