Science (English Medium) Class 12 - CBSE Question Bank Solutions for Physics

A wire of length 50 cm moves with a velocity of 300 m/min, perpendicular to a magnetic field. If the e.m.f. induced in the wire is 2 V, the magnitude of the field in tesla is ______.

Equipotential surfaces ______.

Ampere’s circuital law is given by _______.

Two identical current carrying coaxial loops, carry current I in opposite sense. A simple amperian loop passes through both of them once. Calling the loop as C, then which statement is correct?

Which of the following is NOT the property of equipotential surface?

The emf induced across the ends of a conductor due to its motion in a magnetic field is called motional emf. It is produced due to magnetic Lorentz force acting on the free electrons of the conductor. For a circuit shown in the figure, if a conductor of length l moves with velocity v in a magnetic field B perpendicular to both its length and the direction of the magnetic field, then all the induced parameters are possible in the circuit.

Direction of current induced in a wire moving in a magnetic field is found using ______.

The emf induced across the ends of a conductor due to its motion in a magnetic field is called motional emf. It is produced due to magnetic Lorentz force acting on the free electrons of the conductor. For a circuit shown in the figure, if a conductor of length l moves with velocity v in a magnetic field B perpendicular to both its length and the direction of the magnetic field, then all the induced parameters are possible in the circuit.

A conducting rod of length l is moving in a transverse magnetic field of strength B with velocity v. The resistance of the rod is R. The current in the rod is ______.

The emf induced across the ends of a conductor due to its motion in a magnetic field is called motional emf. It is produced due to magnetic Lorentz force acting on the free electrons of the conductor. For a circuit shown in the figure, if a conductor of length l moves with velocity v in a magnetic field B perpendicular to both its length and the direction of the magnetic field, then all the induced parameters are possible in the circuit.

A 0.1 m long conductor carrying a current of 50 A is held perpendicular to a magnetic field of 1.25 mT. The mechanical power required to move the conductor with a speed of 1 ms^-1 is ______.

The emf induced across the ends of a conductor due to its motion in a magnetic field is called motional emf. It is produced due to magnetic Lorentz force acting on the free electrons of the conductor. For a circuit shown in the figure, if a conductor of length l moves with velocity v in a magnetic field B perpendicular to both its length and the direction of the magnetic field, then all the induced parameters are possible in the circuit.

A bicycle generator creates 1.5 V at 15 km/hr. The EMF generated at 10 km/hr is ______.

Consider two different hydrogen atoms. The electron in each atom is in an excited state. Is it possible for the electrons to have different energies but same orbital angular momentum according to the Bohr model? Justify your answer.

Derive an expression for the frequency of radiation emitted when a hydrogen atom de-excites from level n to level (n – 1). Also show that for large values of n, this frequency equals to classical frequency of revolution of an electron.

Consider a uniform electric field in the ẑ direction. The potential is a constant ______.

1. in all space.
2. for any x for a given z.
3. for any y for a given z.
4. on the x-y plane for a given z.

Equipotential surfaces ______.

1. are closer in regions of large electric fields compared to regions of lower electric fields.
2. will be more crowded near sharp edges of a conductor.
3. will be more crowded near regions of large charge densities.
4. will always be equally spaced.

The work done to move a charge along an equipotential from A to B ______.

1. cannot be defined as `- int_A^B E.dl`
2. must be defined as `- int_A^B E.dl`
3. is zero.
4. can have a non-zero value.

Prove that a closed equipotential surface with no charge within itself must enclose an equipotential volume.

Find the equation of the equipotentials for an infinite cylinder of radius r₀, carrying charge of linear density λ.

Two identical current carrying coaxial loops, carry current I in an opposite sense. A simple amperian loop passes through both of them once. Calling the loop as C ______.

1. `oint B.dl = +- 2μ_0I`
2. the value of `oint B.dl` is independent of sense of C.
3. there may be a point on C where B and dl are perpendicular.
4. B vanishes everywhere on C.

An e.m.f is produced in a coil, which is not connected to an external voltage source. This can be due to ______.

1. the coil being in a time varying magnetic field.
2. the coil moving in a time varying magnetic field.
3. the coil moving in a constant magnetic field.
4. the coil is stationary in external spatially varying magnetic field, which does not change with time.