Dual Nature of Radiation and Matter — Physics STD 12 Science — Question

A rectangular coil of 300 turns has an average area of average area of 25 cm × 10 cm. The coil rotates with a speed of 50 cps in a uniform magnetic field of strength 4   about an axis perpendicular of the field. The peak value of the induced e.m.f. is (in volt)

(a) 3000 π

(b) 300 π

(c) 30 π

(d) 3 π

In case of a bar magnet, lines of magnetic induction:

Which of the following is wrong statement about binding energy?

The valence of the impurity atom that is to be added to germanium crystal so as to make it a N-type semiconductor, is

(a) 6

(b) 5

(c) 4

(d) 3

A particle of mass m and charge q moves with a constant velocity v along the positive x direction. It enters a region containing a uniform magnetic field B directed along the negative z direction, extending from  x = a to x = b. The minimum value of v required so that the particle can just enter the region x > b  is

(a) qb B/m

(b) q(b – a) B/m

(c) qaB/m

(d) q(b + a)B/2m

A transformer has turn ratio 100/1. If secondary coil has 4 amp current then current in primary coil is

(a) 4 A

(b) 0.04 A

(c) 0.4 A

(d) 400 A

Ge and Si diodes conduct at 0.3 V and 0.7 V respectively. In the following figure if Ge diode connection are reversed, the valve of V₀ changes by

(a) 0.2 V

(b) 0.4 V

(c) 0.6 V

(d) 0.8 V

The radioactivity of a certain radioactive element drops to 1/64 of its initial value in 30 seconds. Its half life is

(a) 2 seconds

(b) 4 seconds

(c) 5 seconds

(d) 6 seconds

The negative Zn pole of a Daniel cell, sending a constant current through a circuit, decreases in mass by 0.13g in 30 minutes. If the electrochemical equivalent of Zn and Cu are 32.5 and 31.5 respectively, the increase in the mass of the positive Cu pole in this time is

(a) 0.242 g

(b) 0.190 g

(c) 0.141 g

(d) 0.126 g

A point object O is placed on the principal axis of a convex lens of focal length f = 20cm at a distance of 40cm to the left of it. The diameter of the lens is 10cm. An eye is placed 60cm to right of the lens and a distance h below the principal axis. The maximum value of h to see the image is:

1. 0
2. 2.5cm
3. 5cm
4. 10cm.