An electric bulb marked 40 W and 200 V, is used in a circuit of supply voltage 100 V. Now its power is
100 W
20 W
40 W
10 W
The magnetic needle of a tangent galvanometer is deflected at an angle 30° due to a magnet. The horizontal component of earth's magnetic field 0.34 x 10-4 T is along the plane of the coil. The magnetic intensity is
1.96 × 10-4 T
1.96 × 104 T
1.96 × 10-5 T
1.96 × 105 T
C.
1.96 × 10-5 T
Angle through which magnet is deflected (θ) = 30°
and horizontal magnetic field (BH) = 0.34 × 10-4 T
Magnetic intensity = BH tanθ
= 034 × 10-4 × tan30°
= (0.34 × 10-4 ) × 0.577
Magnetic intensity = 1.96 × 10-5 T
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
Assertion: The quantity L/R possesses dimension of time.
Reason: To reduce the rate of increase of current through a solenoid, we should increase the time constant ( L/R ).
If both the assertion and reason are true and reason is a correct explanation of assertion
If both assertion and reason are true but assertion is not correct explanation of the assertion
If the assertion is true but the reason is false.
If both assertion and reason are false.
Assertion: In a simple battery circuit, the point of the lowest potential is positive terminal of the battery.
Reason: The current flows towards the point of the higher potential, as it does in such a circuit from the negative to the positive terminal.
If both the assertion and reason are true and reason is a correct explanation of the assertion.
If both the assertion and reason are true and reason 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.
Assertion: We use a thick wire in the secondary of a step down transformer to reduce the production heat.
Reason: When the plane of the armature is parallel to the line of force of magnetic field, the magnitude of induced e.m.f. is maximum.
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
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
Assertion: Faraday's laws are consequences of conservation of energy.
Reason: In a purely resistive A.C. circuit, the current lags behind the e.m.f. in phase.
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.