List of top Physics Questions asked in CBSE CLASS XII

A telescope has an objective lens of focal length 144 cm and an eyepiece of focal length 6.0 cm. The magnifying power and the length of telescope tube will be respectively :

A square loop of side 50 cm is placed in a uniform magnetic field of 3.0 T acting perpendicular to the plane of the loop. If the loop is rotated through an angle of $90^\circ$ in 0.3 s, the value of emf induced in the loop would be :

Why electric field $\vec{E}$ at a point on an equipotential surface must be perpendicular to the surface at that point ?

In the given figure, a steady current I flows through the circuit when points A and C are connected by a wire of negligible resistance. Find the potential difference between points B and C.

The process named ‘minority carrier injection’ in a p-n junction diode occurs during :

Use Kirchhoff’s rules to find the current through $3\,\Omega$ resistor in the circuit shown in the figure.

Use Kirchhoff’s rules to find the current through $3\,\Omega$ resistor in the circuit shown in the figure.

Use Kirchhoff’s rules to find the current through $3 \Omega$ resistor in the circuit shown in the figure :

A ray of light in air is incident at angle $i$ on a face of an equilateral glass prism and is refracted through the prism. As $i$ is varied, it is observed that the ray undergoes minimum deviation, when the $i$ is three-fourth of the angle of the prism. Calculate the speed of light in the prism.

A magnet held vertically, with its north pole down, is dropped along the axis of a closed solenoid placed vertically on a table. If the observer looks down from the top,

What are coherent sources ? Why they are necessary for observing stable interference pattern ? Draw a graph showing the variation of intensity of light with the position on the screen in Young's double-slit experiment.

Find the net resistance of the network of resistors connected between $A$ and $B$, as shown in the figure.

Find the net resistance of the network of resistors connected between $A$ and $B$, as shown in the figure.

Two large thin plane sheets, each having surface charge density $\sigma$, are held close and parallel to each other in air. What is the net electric field at a point (i) inside and (ii) outside the sheets ?

Two heaters rated as $(P_1, V)$ and $(P_2, V)$ are connected in series across a dc source of $\dfrac{V}{2}$ volt. The power consumed by the combination will be –

The ‘distance of closest approach’ of an alpha-particle is ‘$d$’ when it moves with a velocity $v$ head-on towards the target nucleus. If the velocity of alpha particle is halved, the new ‘distance of closest approach’ will be –

In a series LCR circuit, the voltage across the resistor, capacitor and inductor is $10\ \text{V}$ each. If the capacitor is short circuited, the voltage across the inductor will be

An electromagnetic wave passes from vacuum into a dielectric medium with relative electrical permittivity $\dfrac{3}{2}$ and relative magnetic permeability $\dfrac{8}{3}$. Then, its

The distance-of-closest-approach for an alpha particle is '$d$' when it moves head-on with speed $v$ towards a target nucleus. If the alpha particle is replaced by a proton moving with the same speed, the new distance-of-closest-approach will be:

(i) Answer the following giving reason:

(I) The electron drift speed is estimated to be only a few mm/s for currents in the range of a few amperes. How, then, is the current established almost the instant a circuit is closed?

(II) A low voltage supply from which one needs high currents must have very low internal resistance. Why?

(III) The assertion that V = IR is a statement of Ohm's law is not true. Why?

(ii) Two cells of emfs 12 V and 6 V are connected in parallel as shown in the figure. Their internal resistances are 1 $\Omega$ and 0.5 $\Omega$ respectively. Calculate the emf and internal resistance of the equivalent cell between points A and B.

(i) Define the terms (I) resonant frequency, and (II) power factor of a series LCR circuit. For what value of the power factor will the power dissipated in the circuit be maximum?

(ii) An inductor of $\dfrac{5}{\pi}$ H, a capacitor of $\dfrac{50}{\pi}\ \mu\text{F}$ and a resistor of $400\ \Omega$ are connected in series across an ac voltage $v = 140 \sin(100\pi t)$ V. Calculate:

(I) impedance of the circuit, and

(II) rms value of current that flows in the circuit.

(Take $\sqrt{2} = 1.4$)

Radiation of wavelength 331 nm irradiates the following metals:

Metal	Work Function (eV)
Na	1.92
K	2.15
Ca	3.20
Mo	4.17

Which of the following statements is correct?

Which of the following p-n junction diodes is forward biased?

An equiconvex lens of focal length $15$ cm is cut into two equal plano-convex halves. The focal length of each half will be: