CBSE
Multiple Choice QuestionsA metal rod consumes power P on passing current. If it is cut into two half and joined in parallel, it will consume power
P
2P
P/4
Assertion: We cannot think of a magnetic field configuration with three poles.
Reason: A bar magnet does exert a torque on itself due to its own field.
If both the assertion and reason are true and reason is a correct explanation of the assertion.
If both assertion and reason are true but assertion is not a correct explanation of the assertion.
If the assertion is true but the reason is false.
If both assertion and reason are false
The difference in lengths of a mean solar day and a sideral day is about
1 min
4 min
15 min
56 min
The earth's magnetic field at a given point is 0.5 × 10-5 Wb/m2. This field is to be annulled by magnetic induction at the centre of a circular conducting loop of radius 5.0 cm. The current required to be flown in the loop nearly
0.2 A
0.4 A
4 A
40 A
In moving coil galvanometer, the magnetic field used is
non-uniform
radial
uniform
None of these
The coefficient of mutual inductance, when magnetic flux changes by 2 x 10-2 Wb and current changes by 0.01 A is
2 H
4 H
3 H
8 H
At a place earth's magnetic field, 5 × 105 Wb/m2 is acting perpendicular to a coil of radius R = 5 cm. If μο / 4 = 107 , then how much current is induced in circular loop?
0.2 A
0 A
4 A
40 A
When a galvanometer is shunted by resistance S, its current capacity increases n times. If the same galvanometer is shunted by another resistance S', its current capacity will increase by n' is given by
A wire length l carries a steady current. It is bent first to form a circular plane loop of one turn. The magnetic field at the centre of the loop is B. The same length is now bent more sharply give a to double loop of smaller radius. The magnetic field at the centre caused by the same is
B
B/4
4B
B/2
Three charges are placed at the vertices of an equilateral triangle of side a as shown in the given figure. The force experienced by the charge placed at the vertex A in a direction normal to BC is
Q2 / 4πε0a2
- Q2 (4πε0a2<)
zero
Q2 / 2πε0a2
