Nuclei — Physics STD 12 Science — Question

When a glass rod is rubbed with silk, what kind of charge will be developed on glass?

An attractive force of 9N acts between +5C and −5C at some distance. These charges are allowed to touch each other and are then again placed at their initial position. The force acting between them will be:

Each plate of a parallel plate capacitor has a charge q on it. The capacitor is now connected to a batter. Now:

An under water swimmer is at a depth of 12 m below the surface of water.  A bird is at a height of 18 m from the surface of water, directly above his eyes.  For the swimmer the bird appears to be at a distance from the surface of water equal to (Refractive Index of water is 4/3)

(a) 24 m

(b) 12 m

(c) 18 m

(d) 9 m

The activity of a radioactive sample is measured as 9750 counts per minute at t = 0 and as 975 counts per minute at t = 5 minutes. The decay constant is approximately

(a) 0.230 per minute	(b) 0.461 per minute
(c) 0.691 per minute	(d) 0.922 per minute

Three identical capacitors are combined differently. For the same voltage to each combination, the one that stores the greatest energy is

(a) Two in parallel and the third in series with it	(b) Three in series
(c) Three in parallel	(d) Two in series and third in parallel with it

A heater coil is cut into two parts of equal length and one of them is used in the heater. The ratio of the heat produced by this half coil to that by the original coil is

(a) 2 : 1

(b) 1 : 2

(c) 1 : 4

(d) 4 : 1

The figure below shows currents in a part of electric circuit. The current i is

(a) 1.7 amp

(b) 3.7 amp

(c) 1.3 amp

(d) 1 amp

If there is no external force acting on a nonrigid body, which of the following quantities must remain constant?

1. Angular momentum.
2. Linear momentum.
3. Kinetic energy.
4. Moment of inertia.