CBSE Board exam are coming in February. So, I have brought CBSE Board Class 12 Physics Important Questions 2024 which are being asked the same for last 3-4 years. Try to solve these questions for securing high marks in your board examinations.
You can also check the Important Questions for English, Chemistry, Hindi and Other Subjects
CBSE Board Class 12 Physics Important Questions 2024: Objective
1. A metallic plate exposed to white light emits electrons. For which of the following colours of light, the stopping potential will be maximum?
(A) Blue
(B( Yellow
(C) Red
(D) Violet
2. When alpha particles are sent through a thin gold foil, most of them go straight through the foil, because:
(A) Alpha particles are positively charged
(B) The mass of an alpha particle is more than the mass of an electron
(C) Most of the part of an atom is empty space
(D) Alpha particles move with high velocity
3. An electron is moving along positive x-axis in a magnetic field which is parallel to the positive y-axis. In what direction will the magnetic force be acting on the electron?
(A) Along – x axis
(B) Along – z axis
(C) Along +z axis
(D) Along – y axis
4. The relative magnetic permeability of a substance X is slightly less than unity and that of substance Y is slightly more than unity, then.
(A) X is paramagnetic and Y is ferromagnetic
(B) X is diamagnetic and Y is ferromagnetic
(C) X and Y both are paramagnetic
(D) X is diamagnetic and Y is paramagnetic
5. An ammeter of resistance 0.81 ohm reads up to 1 A. The value of the required shunt to increase the range to 10 A is:
(A) 0.9 ohm
(B) 0.09 ohm
(C) 0.03 ohm
(D) 0.3 ohm
6. The large scale transmission of electrical energy over long distances is done with the use of transformers. The voltage output of the generator is stepped-up because of:
(A) Reduction of current
(B) Reduction of current and voltage both
(C) Power loss is cut down
(D) (a) and (c) both
7. In a coil of resistance 100 Ωa current is induced by changing the magnetic flux through it. The variation of current with time is as shown in the figure. The magnitude of change in flux through coil is:
(A) 200 Wb
(B) 275 Wb
(C) 225 Wb
(D 250 Wb
8. Read the following paragraph and answer the questions that follow. A semiconductor diode is basically a p-n junction with metallic contacts provided at the ends for the application of an external voltage. It is a two terminal device. When an external voltage is applied across a semiconductor diode such that p-side is connected to the positive terminal of the battery and n-side to the negative terminal, it is said to be forward biased. When an external voltage is applied across the diode such that n-side is positive and p-side is negative, it is said to be reverse biased. An ideal diode is one whose resistance in forward biasing is zero and the resistance is infinite in reverse biasing. When the diode is forward biased, it is found that beyond forward voltage called knee voltage, the conductivity is very high. When the biasing voltage is more than the knee voltage the potential barrier is overcome and the current increases rapidly with increase in forward voltage. When the diode is reverse biased, the reverse bias voltage produces a very small current about a few micro amperes which almost remains constant with bias. This small current is reverse saturation current.
(I) In the given figure, a diode D is connected to an external resistance R = 100 Ω and an emf of 3.5 V. If the barrier potential developed across the diode is 0.5 V, the current in the circuit will be:
(A) 40 mA
(B) 20 mA
(C) 35 mA
(D) 30 mA
(ii) Based on the V-I characteristics of the diode, we can classify diode as:
(A) Bilateral device
(B) Ohmic device
(C) Non-ohmic device
(D) Passive element
(iii) The V-I characteristic of a diode is shown in the figure. The ratio of the resistance of the diode at I = 15mA to the resistance at V = – 10V is.
(A) 100
(B) 10-6
(C) 106
(D) 10
CBSE Board Class 12 Physics Important Questions 2024: Subjective
1. Draw the pattern of electric field lines, when a point charge – Q is kept near an uncharged conducting plate.
2. How does the mobility of electrons in a conductor change, if the potential difference applied across the conductor is doubled, keeping the length and temperature of the conductor constant ?
3. Define the term “threshold frequency”, in the context of photoelectric emission.
4. Define the term “Intensity” in photon picture of electromagnetic radiation.
5. What is the speed of light in a denser medium of polarising angle 30° ?
6. In sky wave mode of propagation, why is the frequency range of transmitting signals restricted to less than 30 MHz ?
7. On what factors does the range of coverage in ground wave propagation depend?
8. Calculate the radius of curvature of an equi-concave lens of refractive index 1.5, when it is kept in a medium of refractive index 1.4, to have a power of -5D?
9. An equilateral glass prism has a refractive index 1.6 in air. Calculate the angle of minimum deviation of the prism, when kept in a medium of refractive index 4 2/5.
10. An Alpha -particle and a proton of the same kinetic energy are in turn allowed to pass through a magnetic field B, acting normal to the direction of motion of the particles. Calculate the ratio of radii of the circular paths described by them.
11. State Bohr’s quantization condition of angular momentum. Calculate the shortest wavelength of the Bracket series and state to which part of the electromagnetic spectrum does it belong.
12. Calculate the orbital period of the electron in the first excited state of hydrogen atom.
13. Why a signal transmitted from a TV tower cannot be received beyond a certain distance ? Write the expression for the optimum separation between the receiving and the transmitting antenna.
14. Why is wave theory of electromagnetic radiation not able to explain photo electric effect ? How does photon picture resolve this problem?
15. Define the term wavefront. Using Huygen’s wave theory, verify the law of reflection.
16. Define the term, “refractive index” of a medium. Verify Snell’s law of refraction when a plane wavefront is propagating from a denser to a rarer medium.
17. Draw a labelled ray diagram of an astronomical telescope in the near point adjustment position. A giant refracting telescope at an observatory has an objective lens of focal length 15 m and an eyepiece of focal length 1.0 cm. If this telescope is used to view the Moon, find the diameter of the image of the Moon formed by the objective lens. The diameter of the Moon is 3.48 × 10^6 m, and the radius of lunar orbit is 3.8 × 10^8 m
18. Write three points of differences between para-, dia- and ferro- magnetic materials, giving one example for each.
19. Define the term ‘decay constant’ of a radioactive sample. The rate of disintegration of a given radioactive nucleus is 10000 disintegrations/s and 5,000 disintegrations/s after 20 hr. and 30 hr. respectively from start. Calculate the half life and initial number of nuclei at t = 0.
20. Draw the circuit diagram of a full wave rectifier and explain its working. Also, give the input and output waveforms.
21. What are permanent magnets ? Give one example.
22. What is the geometrical shape of equipotential surfaces due to a single isolated charge ?
23. Which of the following waves can be polarized
(i) Heat waves
(ii) Sound waves? Give reason to support your answer.
24. A capacitor has been charged by a dc source. What are the magnitude of conduction and displacement current, when it is fully charged?
25. Write the relationship between angle of incidence ‘i’, angle of prism ‘A’ and angle of minimum deviations Am for a triangular prism.
26. The emf of a cell is always greater than its terminal voltage. Why? Give reason.
27. metallic rod of length ‘/’ is rotated with a frequency with one end hinged at the centre and the other end at the circumference of a circular metallic ring of radius r, about an axis passing through the centre and perpendicular to the plane of the ring. A constant uniform magnetic field B parallel to the axis is present every where. Using Lorentz force, explain how emf is induced between the centre and the metallic ring and hence obtain the expression for it.
28. Two spherical bobs, one metallic and the other of glass, of the same size are allowed to fall freely from the same height above the ground. Which of the two would reach earlier and why?
29. Out of the two magnetic materials, ‘A’ has relative permeability slightly greater than unity while ‘B’ has less than unity. Identify the nature of the materials ‘A’ and ‘B’. Will their susceptibilities be positive or negative?
30. State Kirchhoff’s rules. Explain briefly how these rules are justified.
31. A capacitor ‘C’, a variable resistor ‘R’ and a bulb ‘B’ are connected in series to the ac mains in circuit as shown. The bulb glows with some brightness. How will the glow of the bulb change if
(i) a dielectric slab is introduced between the plates of the capacitor, keeping resistance R to be the same;
(ii) the resistance R is increased keeping the same capacitance ?
32. An electric dipole of length 4 cm, when placed with its axis making an angle of 60° with a uniform electric field, experiences a torque of 4√3 Nm. Calculate the potential energy of the dipole, if it has charge ± 8 nC.
33. Name the phenomenon which shows the quantum nature of electromagnetic radiation.
34. A 12-5 eV electron beam is used to excite a gaseous hydrogen atom at room temperature. Determine the wavelengths and the CHA corresponding series of the lines emitted.
