Multiple Choice QuestionsThe angle of dip at the poles and the equator respectively are
30o, 60o
0o, 90o
45o, 90o
90o, 0o
A hexagon of side 8 cm has a charge 4 µC at each of its vertices. The potential at the centre of the hexagon is
2.7 × 106 V
7.2 × 1011 V
2.5 × 1012 V
3.4 × 104 V
The self-inductance of a coil having 400 turns is 10 mH. The magnetic flux through the cross-section of the coil corresponding to current 2 mA is
2 × 10-5 Wb
2 × 10-3 Wb
3 × 10-5 Wb
8 × 10-3 Wb
A 5 µF capacitor is charged by being connected to a 3 V battery. The battery is then disconnected. If the resistance of the dielectric material between the capacitor plates is 109 Ω, what is the charge remaining on the capacitor 1 h after it has been disconnected ?
1.5 × 10-5 C
7.4 × 10-6 C
5.4 × 10-6 C
8.4 × 10-5 C
A coil of inductance 8 μH is connected to a capacitor of capacitance 0.02 μF To what wavelength is this circuit tuned?
7.54 × 103 m
4.12 × 102 m
15.90 × 103 m
7.54 × 102 m
A metallic solid sphere is placed in a uniform electric field. Which path, the lines of force follow as shown in figure?
1
2
3
4
Assertion: An emf E is induced in a closed loop when magnetic flux is varied. The induced electric field E is not a conservative field.
Reason: The line integral around the closed loop is non-zero.
If both assertion and reason are true and reason is the correct explanation of assertion.
If both assertion and reason are true but reason is not the correct explanation of assertion.
If assertion is true but reason is false.
If both assertion and reason are false.
Assertion: UV radiation causes photodissociation of ozone into O2 and O, thus causing damage to the stratospheric ozone layer.
Reason: Ozone hole is resulting in global warming and climate change.
If both assertion and reason are true and reason is the correct explanation of assertion.
If both assertion and reason are true but reason is not the correct explanation of assertion.
If assertion is true but reason is false
If both assertion and reason are false
Assertion: Electromagnetic waves with frequencies smaller than the critical frequencies of ionosphere cannot be used for communication using sky wave propagation.
Reason: The refractive index of the ionosphere becomes very high for frequencies higher than the critical frequency.
If both assertion and reason are true and reason is the correct explanation of assertion.
If both assertion and reason are true but reason is not the correct explanation of assertion.
If assertion is true but reason is false.
If both assertion and reason are false.
Assertion: When a magnetic dipole is placed in a non uniform magnetic field, only a torque acts on the dipole.
Reason: Force would act on dipole if magnetic field is uniform.
If both assertion and reason are true and reason is the correct explanation of assertion.
If both assertion and reason are true but reason is not the correct explanation of assertion
If assertion is true but reason is false.
If both assertion and reason are false.
D.
If both assertion and reason are false.
When dipole is placed uniformly electric field and dipole vector direction is not parallel to field direction, each charge of dipole experiences a force. The magnitude of the two forces are equal but opposite in direction. These equal and unlike give rise to couple. This couple gives a torque to dipole, which rotates the dipole and makes it align to the direction of a field. Once the dipole is aligned in the direction of field, torque vanishes ( r × F will be zero, if r and F are in same direction). Once the dipole is aligned to electric field, the net force will be zero because they are in opposite direction. Hence in uniform field dipole experiences only torque.
When a dipole is placed in non-uniform field, there will be torque as explained above. But once the dipole is aligned to field direction, the forces acting on the charges are not same. Hence there will be a net force acting on the dipole in the direction of magnetic field. Hence in non-uniform field, electric dipole experiences both torque and force.
Switch
