Current Electricity — Physics STD 12 Science — Question

The reading of the ammeter as per figure shown is

(a)

(b)

(c)

(d) 2 A

For a cell of e.m.f. 2V, a balance is obtained for 50 cm of the potentiometer wire. If the cell is shunted by a  2Ω resistor and the balance is obtained across 40 cm of the wire, then the internal resistance of the cell is

(a) 0.25 Ω

(b) 0.50 Ω

(c) 0.80 Ω

(d) 1.00 Ω

A dielectric slab is inserted between the plates of an isolated charged capacitor. Which of the following quantities will remain the same?

1. The electric field in the capacitor.
2. The charge on the capacitor.
3. The potential difference between the plates.
4. The stored energy in the capacitor.

If the wavelength of the first line of the Balmer series of hydrogen is 6561 , the wavelength of the second line of the series should be

(a) 13122

(b) 3280

(c) 4860

(d) 2187

The forbidden energy gap for germanium crystal at 0 K is:

An electric dipole placed in a non-uniform electric field can experience

A vibration magnetometer consists of two identical bar magnets placed one over the other such that they are perpendicular and bisect each other. The time period of oscillation in a horizontal magnetic field is  seconds. One of the magnets is removed and if the other magnet oscillates in the same field, then the time period in seconds is

(a)

(b)

(c) 2

(d)

The magnetic lines of force inside a bar magnet:

Variation of current passing through a conductor as the voltage applied across its ends as varied is shown in the adjoining diagram. If the resistance (R) is determined at the points A, B, C and D, we will find that

(a) RC = RD

(b) RB > RA

(c) RC > RB

(d) None of these

A negatively charged plate has charge density of 2 . The initial distance of an electron which is moving toward plate, cannot strike the plate, if it is having energy of 200 eV

(a) 1.77 mm

(b) 3.51 mm

(c) 1.77 cm

(d) 3.51 cm