CBSE
A 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
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
The difference in lengths of a mean solar day and a sideral day is about
1 min
4 min
15 min
56 min
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
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
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
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
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
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
In moving coil galvanometer, the magnetic field used is
non-uniform
radial
uniform
None of these