Explanation:
Force will decreases because when medium is inserted between then it will reduces the forces by its permitivity. the force becomes
$\text{Fe}_\text{m}=\frac{\text{Fe}}{\in_\text{r}}$
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A ray passes through a prism of angle 60° in minimum deviation position and suffers a deviation of 30°. What is the angle of incidence on the prism
|
(a) 30° |
(b) 45° |
(c) 60° |
(d) 90° |
The equivalent inductance of two inductances is 2.4 henry when connected in parallel and 10 henry when connected in series. The difference between the two inductances is
|
(a) 2 henry |
(b) 3 henry |
(c) 4 henry |
(d) 5 henry |
The armature of dc motor has 20Ω resistance. It draws current of 1.5 ampere when run by 220 volts dc supply. The value of back e.m.f. induced in it will be
|
(a) 150 V |
(b) 170 V |
(c) 180 V |
(d) 190 V |
Larger aperture of objective lens in an astronomical telescope:
It is desired to photograph the image of an object placed at a distance of 3m from the plane mirror. The camera which is at a distance of 4.5 m from the mirror should be focussed for a distance of
| (a) 3m | (b) 4.5m | (c) 6m | (d) 7.5 m |
An arbitrary shaped closed coil is made of a wire of length L and a current I ampere is flowing in it. If the plane of the coil is perpendicular to magnetic field 
, the force on the coil is
|
(a) Zero |
(b) IBL |
(c) 2IBL |
(d) |
