Atoms — Physics STD 12 Science — Question

If a resistance  is connected in parallel with the resistance R in the circuit shown, then possible value of current through R and the possible value of   will be

(a)

(b) I, 2R

(c)

(d)

Consider the following statements A and B and identify the correct choice of the given answers

A : The width of the depletion layer in a P-N junction diode increases in forwards bias

B : In an intrinsic semiconductor the fermi energy level is exactly in the middle of the forbidden gap

(a) A is true and B is false	(b) Both A and B are false
(c) A is false and B is true	(d) Both A and B are true

The resistance of 1 A ammeter is 0.018 Ω . To convert it into 10 A ammeter, the shunt resistance required will be

(a) 0.18 Ω

(b) 0.0018 Ω

(c) 0.002 Ω

(d) 0.12 Ω

Unit of magnetic field is :

The resistance of a metal increases with increasing temperature because:

Huygen wave theory allows us to know

(a) The wavelength of the wave	(b) The velocity of the wave
(c) The amplitude of the wave	(d) The propagation of wave fronts

An X-ray machine has an accelerating potential difference of 25,000 volts. By calculation the shortest wavelength will be obtained as  (h = 6.63 ; e =  coulomb)

(a) 0.25 Å

(b) 0.50 Å

(c) 1.00 Å

(d) 2.50 Å

In comparison to a half wave rectifier, the full wave rectifier gives lower

(a) Efficiency	(b) Average dc
(c) Average output voltage	(d) None of these

The de-Broglie wavelength of a neutron at 27^oC is l. What will be its wavelength at 927^oC

(a) l / 2

(b) l / 3

(c) l / 4

(d) l / 9

The electron in a hydrogen atom makes a transition from an excited state to the ground state. Which of the following statements is true

(a) Its kinetic energy increases and its potential and total energies decrease

(b) Its kinetic energy decreases, potential energy increases and its total energy remains the same

(c) Its kinetic and total energies decrease and its potential energy increases

(d) Its kinetic, potential and total energies decreases