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

If an electron is moving with velocity `vecnu` produces a magnetic field `vec"B"`, then ______.

Which of the following property shows the property of ferromagnetic substances?

Two identical bar magnets are fixed with their centres at a distance d apart. A stationary charge Q is placed at P in between the gap of the two magnets at a distance D from the centre O as shown in the figure. The force on the charge Q is ______.

Which of the following statements is not correct?

In general, metallic ropes are suspended on the carriers taking inflammable materials. The reason is ______.

When 10¹⁴ electrons are removed from a neutral metal sphere, the charge on the sphere becomes ______.

Two similar spheres having +Q and -Q charges are kept at a certain distance. F force acts between the two. If at the middle of two spheres, another similar sphere having +Q charge is kept, then it experiences a force in magnitude and direction as ______.

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

A 20 volt AC is applied to a circuit consisting of a resistance and a coil with negligible resistance. If the voltage across the resistance is 12 volt, the voltage across the coil is ______.

Assertion(A): A proton and an electron, with same momenta, enter in a magnetic field in a direction at right angles to the lines of the force. The radius of the paths followed by them will be same.

Reason (R): Electron has less mass than the proton.

Select the most appropriate answer from the options given below:

In a pure semiconductor crystal of Si, if antimony is added then what type of extrinsic semiconductor is obtained. Draw the energy band diagram of this extrinsic semiconductor so formed.

Explain how does (i) photoelectric current and (ii) kinetic energy of the photoelectrons emitted in a photocell vary if the frequency of incident radiation is doubled, but keeping the intensity same?

Show the graphical variation in the above two cases.

The Electric field at a point is ______.

1. always continuous.
2. continuous if there is no charge at that point.
3. discontinuous only if there is a negative charge at that point.
4. discontinuous if there is a charge at that point.

Five charges, q each are placed at the corners of a regular pentagon of side ‘a’ (Figure).

(a) (i) What will be the electric field at O, the centre of the pentagon?

(ii) What will be the electric field at O if the charge from one of the corners (say A) is removed?

(iii) What will be the electric field at O if the charge q at A is replaced by –q?

(b) How would your answer to (a) be affected if pentagon is replaced by n-sided regular polygon with charge q at each of its corners?

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.

Is the momentum conserved when charge crosses a junction in an electric circuit? Why or why not?