Electromagnetic Waves — Physics STD 12 Science — Question

The magnetic moment of a current (l) carrying circular coil of radius (r) and number of turns (n) varies as

In an electron gun the control grid is given a negative potential relative to cathode in order to:

The direction of ray of light incident on a concave mirror is shown by PQ while directions in which the ray would travel after reflection is shown by four rays marked 1, 2, 3 and 4 (Fig). Which of the four rays correctly shows the direction of reflected ray?

For which of the following colour, the magnifying power of a microscope will be maximum

(a) White colour

(b)  Red colour

(c) Violet colour

(d)  Yellow colour

The magnitude of the electric field is given by the change in magnitude of potential per unit displacement _____ to the equipotential surface at the point.

If the capacitors in the previous question are joined in parallel, the capacitance and the breakdown voltage of the combination will be:

1. 2C and 2V
2. C and 2V
3. 2C and V
4. C and V

The order of magnitude of radius of nucleus is ___________.

Direction of induced emf is determined by:

State which of the following is correct

(a) Joule = coulomb × volt	(b)  Joule = coulomb/volt
(c) Joule = volt × ampere	(d) Joule = volt/ampere

A capacitor 4 μF charged to 50  V is connected to another capacitor of 2 μF  charged to 100 V with plates of like charges connected together. The total energy before and after connection in multiples of  (  is

(a) 1.5 and 1.33

(b) 1.33 and 1.5

(c) 3.0 and 2.67

(d) 2.67 and 3.0