Alternating Current — Physics STD 12 Science — Question

A thin converging lens is formed with one surface convex and the other plane. Does the position of image depend on whether the convex surface or the plane surface faces the object?

The instantaneous current and voltage of an a.c. circuit are given by
i = 10 sin 300t A and v = 200 sin 300t V
What is the power dissipation in the circuit?

State de-Broglie hypothesis.

Answer the following:
The top of the atmosphere is at about 400kV with respect to the surface of the earth, corresponding to an electric field that decreases with altitude. Near the surface of the earth, the field is about 100Vm^–1. Why then do we not get an electric shock as we step out of our house into the open? (Assume the house to be a steel cage so there is no field inside!)

Name the EM waves used for studying crystal structure of solids. What is its frequency range?

If the self-inductance of an iron core inductor increases from 0·01mH to 10mH on introducing the iron core into it, what is the relative permeability of the core material used?

When a body is weighed on an ordinary balance we demand that the arm should be horizontal if the weights on the two pans are equal. Suppose equal weights are put on the two pans, the arm is kept at an angle with the horizontal and released. Is the torque of the two weights about the middle point (point of support) zero? Is the total torque zero? If so, why does the arm rotate and finally become horizontal?

Plot a graph showing variation of current versus voltage for the material GaAs.

What is the magnitude of the torque and also give its direction.