Semiconductor Electronics: Materials, Devices and Simple Circuits — Physics STD 12 Science — Question

On increasing the reverse bias to a large value in a PN-junction diode, current

(a) Increases slowly

(b) Remains fixed

(c) Suddenly increases

(d) Decreases slowly

In a transformer the primary has 500 turns and secondary has 50 turns. 100 volts are applied to the primary coil, the voltage developed in the secondary will be

(a) 1 V

(b) 10 V

(c) 1000 V

(d) 10000 V

Two identical charged spherical drops each of capacitance C merge to form a single drop. The resultant capacitance is

(a) Equal to 2C	(b) Greater than 2C
(c) Less than 2C but greater than C	(d) Less than C

With a potentiometer null point were obtained at 140 cm and 180 cm with cells of emf 1.1 V and one unknown X volts. Unknown emf is

(a) 1.1 V

(b) 1.8 V

(c) 2.4 V

(d) 1.41 V

In the figure given the value of X  resistance will be, when the p.d. between B and D is zero

(a) 4 ohm

(b) 6 ohm

(c) 8 ohm

(d) 9 ohm

The positive temperature coefficient of resistance is for

(a) Carbon

(b) Germanium

(c) Copper

(d) An electrolyte

+q, +2q, +3q, +4q, ……(up to +20q) charges are situated at coordinates (0, 0), (1, 0), (2, 0), ….. (Up to 20). What is the total charge stored in the system?

The plate current i_p in a triode valve is given   where i_p is in milliampere and V_p and V_g are in volt. If r_p = 10⁴ ohm, and , then for   and , what is the value of K and grid cut off voltage

(a) – 6V, (30)3/2

(b) -6 V,

(c) + 6V, (30)3/2

(d) + 6V, (1/30)3/2

The radius of curvature of a concave mirror is 0.80 cm, its focal length in meters will be :