Atoms — Physics STD 12 Science — Question

Current in the circuit is wattless, if.

An electron falls from rest through a vertical distance h in a uniform and vertically upward directed electric field E. The direction of electric field is now reversed, keeping its magnitude the same. A proton is allowed to fall from rest in it through the same vertical distance h. The time of fall of the electron, in comparison to the time of fall of the proton is:

If a slab of insulating material 4   thick is introduced between the plates of a parallel plate capacitor, the separation between plates has to be increased by 3.5   to restore the capacity to original value. The dielectric constant of the material will be

(a) 6

(b) 8

(c) 10

(d) 12

An inflated balloon was pressed against a wall after it has been rubbed with a piece of synthetic cloth. It was found that the balloon sticks to the wall. What force might be responsible for the attraction between the balloon and the wall?

Plane figures made of thin wires of resistance R = 50 milli ohm/metre are located in a uniform magnetic field perpendicular into the plane of the figures and which decrease at the rate dB/dt = 0.1 m T/s. Then currents in the inner and outer boundary are. (The inner radius a = 10 cm and outer radius b = 20 cm)

(a) 10– 4 A (Clockwise), 2 × 10– 4 A (Clockwise)

(b) 10– 4 A (Anticlockwise), 2 × 10– 4 A (Clockwise)

(c) 2 × 10– 4 A (clockwise), 10– 4 A (Anticlockwise)

(d) 2 × 10– 4 A (Anticlockwise), 10– 4 A (Anticlockwise)

When a straight wire is moved up and down rapidly between two poles of a horseshoe magnet then _______ is produced in the wire.

Which of the following combinations should be selected for better tuning of an LCR circuit used for communication?

Two electric bulbs whose resistances are in the ratio of 1 : 2 are connected in parallel to a constant voltage source. The powers dissipated in them have the ratio

(a) 1 : 2

(b) 1 : 1

(c) 2 : 1

(d) 1 : 4

AND gate:

Electric field is in the direction in which the potential ____ steepest.