When impurities are added to semi-conductors, the conductivity of the semi-conductor
increases then decreases
increases
decreases
remains constant
Correct answer is B
When impurities are added to semi conductor , the semi conductor is said to be doped, and increases the conductivity of the semi-conductor.
60°
90°
30°
45°
Correct answer is C
The force acting on moving charge in magnetic field is given by: F=q VBSin θ
sin θ =F=(8.0x10)-14/1.6x10-19x1.0x106x1.0 = (8.0x10)14/16 x 1013
(8.0x 10)-14/16x10-14
=0.5000
∴ θ= sin-1 0.5000
=30°
250days
150days
300days
200days
Correct answer is A
Since 1/32, is the fraction left of any radioactive material after 5half lives, that is:
1/32= (1/2)5. Thus if a half life is 50 days, 5 half lives will be 50 x 5= 250 days
In an a.c circuit that contains only a capacitor, the voltage lags behind the current by
180°
90°
60°
30°
Correct answer is B
In a purely capacity circuit, voltage lags behind current by 90°, or current leads voltage by 90°
8 s
4 s
16 s
10 s
Correct answer is B
for a body projected at an angle θ to the horizontal, the time of the flight is given by T = (2u sin θ)/g =(2x 40)x sin (30)/10 =(2 x 40) x (0.5)/10 = 4.0secs.