Electromagnetic Waves — Physics STD 12 Science — Question

. The electric potential inside a conducting sphere _____________?

The magnetic flux in a coil of 100 turns increases by 12 × 10³ Maxwell in 0.2 second due to the motion of a magnet. The emf induced in the coil will be.

After 1α and 2β emissions

(a) Mass number reduces by 3	(b) Mass number reduces by 4
(c) Mass number reduces by 6	(d) Atomic number remains unchanged

Which of the following is an example of a molecule whose centre of mass of positive and negative charges coincide each other?

In an interference experiment, third bright fringe is obtained at a point on the screen with a light of 700 nm. What should be the wavelength of the light source in order to obtain 5th bright fringe at the same point

(a) 500 nm

(b) 630 nm

(c) 750 nm

(d) 420 nm

The chemical equivalent of copper and zinc are 32 and 108 respectively. When copper and silver voltameter are connected in series and electric current is passed through for sometimes, 1.6 g of copper is deposited. Then, the mass of silver deposited will be

(a) 3.5 g

(b) 2.8 g

(c) 5.4 g

(d) None of these

In an RC circuit while charging, the graph of in i versus time is as shown by the dotted line in the diagram figure, where i is the current. When the value of the resistance is doubled, which of the solid curve best represents the variation of in i versus time

(a) P

(b) Q

(c) R

(d) S

An ionization chamber with parallel conducting plates as anode and cathode has 5  electrons and the same number of singly-charged positive ions per . The electrons are moving at 0.4 m/s. The current density from anode to cathode is .  The velocity of positive ions moving towards cathode is

(a) 0.4 m/s

(b) 16 m/s

(c) Zero

(d) 0.1 m/s

A piece of charcoal and a piece of shining steel of the same surface area are kept for a long time in an open lawn in bright sun:

1. The steel will absorb more heat than the charcoal.
2. The temperature of the steel will be higher than that of the charcoal.
3. If both are picked up by bare hands, the steel will be felt hotter than the charcoal.
4. If the two are picked up from the lawn and kept in a cold chamber, the charcoal will lose heat at a faster rate than the steel.

An inductor coil of some resistance is connected to an AC source. Which of the following quantities have zero average value over a cycle?

1. Current.
2. Induced emf in the inductor.
3. Joule heat.
4. Magnetic energy stored in the inductor.