Introduction to Physics — Physics STD 12 Science — Question

A pivoted aluminium bar falls much more slowly through a small region containing a magnetic field than a similar bar of an insulating material. Explain.

A cylinder rolls on a horizontal plane surface. If the speed of the centre is 25m/s, what is the speed of the highest point?

An ordinary electric fan does not cool the air, still it gives comfort in summer. Explain.

The battery discussed in the previous question is suddenly disconnected. Is a current induced in the other loop? If yes, when does it start and when does it end? Do the loops attract each other or repel?

Explain the root mean square value of alternating current.

A point source is placed at a depth h below the surface of water (refractive index = μ).

1. Show that light escapes through a circular area on the water surface with its centre directly above the point source.
2. Find the angle subtended by a radius of the area on the source.

Explain Bohr's atomic model.

When a train starts, the head of a standing passenger seems to be pushed backward. Analyse the situation from the ground frame. Does it really go backward? Coming back to the train frame, how do you explain the backward movement of the head on the basis of Newton's laws?

An immersion heater rated 1000W, 220V is used to heat 0.01m³ of water. Assuming that the power is supplied at 220V and 60% of the power supplied is used to heat the water, how long will it take to increase the temperature of the water from 15^°C to 40^°C?

Explain the difference between electric potential and electrical potential energy and explain the relationship between them.