8
A
Remains samo
Increases
Fluctuates
Decreases
9.
If the forward voltage in a diode is increased, the width of depletion region
Federal Board Past Board Paper 20/20
B
D.
The half life of 191 sr is 9.70 hours. What is decay constant?
A. 1.99x10 *s-
B
1.99x10's.'
D.
The ratio of minimum to maximum wavelength in Balmer series is:
A. 1/4
B.
5/9
D. 5/36
When a battery of cmf "E" and internal resistance "r" is connected across external
1.6x1045-1
1.69x 651
10
3/4
11
1
B.
D.
13.
B.
resistance R, the power consumed in R is max when T/R is
A. 1/2
C.
0
12.
A consequence of Einstein's theory of relativity is:
A.
moving clocks run more slowly than when they are at rest.
B moving rods are longer than when they are at rest.
light exhibits both wave and particle properties.
the laws of physics must appear the same to all observers moving with
uniforın velocity relative to each other.
If input power and output power of an electric motor are 540 W and 382 W
respectively. Then the efficiency is:
A. 100%
91%
C. 71%
D. 51%
14.
A wire has a resistance of 121. It is bent in the form of a circle. The effective
resistance between the two points on any diameter of the circle is:
A. 12Ω
2412
C. 612
D. 302
15.
The constant a of a transistor is 0.95. What would be the change in the collector
current corresponding to a charge of 0.4 mA in the base current in common-
emitter arrangement?
A. 8.6 mA
B. 7.6 mA
C. 10.6 mA
D. 10 mA
B.
16.
The velocity at which the relativistic length of a body reduces to half of its
original length is:
A. V =
B. V =
узс
C. V
D.
V =
2
3c
2
2
C
17.
The speed of electrons in 2nd Bohr orbit is:
A. 1.095 x106m/s
B.
C. 2.19 x 108m/s
D.
1.92 x106m/s
13.6 x107m/s.​