Chhattisgarh Cgbse Class 12 Physics — Real Previous-Year Papers

The phase difference between two points located on the same wavefront is: (a) 2π (b) 0 (c) π (d) π/2

The mass of a photon is: (a) h/v (b) hc/λ (c) h/λ (d) hν/c²

In which part of the electromagnetic spectrum, is the Lyman series of hydrogen found? (a) Ultraviolet (b) Scene (c) Infrared (d) X-rays

The value of barrier potential for Si semiconductor is: (a) 0.3 V (b) 1.1 V (c) 0.7 eV (d) 0.7 V

Write the SI unit of capacitance of capacitor.

What is the resistance of an ideal ammeter?

Can a battery be charged by using alternating current? Write the reason.

Why are convex mirror reflectors used in street lights?

What do you understand by energy band?

Write any two differences between Resistance and Resistivity.

Write any two similarities between Biot-Savart law and Coulomb's law.

What are diamagnetic substances? Write any two properties.

When a magnetic flux of 160 mWb (milliweber) is produced by passing a current of 8A through a coil, then what will be the self-inductance of the coil?

Light waves get polarized while sound waves do not, why?

Write the formula for wavelength of hydrogen atom in the Balmer series and tell in which region of the spectrum this wavelength falls.

What is P-N diode? Draw only the characteristic curve between potential difference and current for a P-N diode.

Find the equivalent capacitance between A and B in the following circuit:

What do you understand by internal resistance of a cell? Establish the formula for internal resistance of the cell. [1+2=3]

What is the wavelength range of X-Ray? Write its two properties. [1+2=3]

What is photoelectric cell or photocell? Write any two uses of photoelectric cells. [1+2=3]

Explain the meanings of the following: (i) Isobar (ii) Binding energy (iii) Nuclear fusion [1+1+1=3]

Write any three differences between N-type semiconductor and P-type semiconductor. [1+1+1=3]

Ramesh is a Class XII student at a rural school. One day, he went for a walk with his friends. A truck passed by with a sign saying, "Caution, Explosive Material". A chain was tied to the truck, touching the ground. Ramesh explained to his friends that as the truck moves, its axis crosses the field lines of a magnetic field of the earth, resulting in an induced electromotive force (EMF) at its ends. The induced charge is channeled through the chain, keeping the explosive material safe. Answer the following questions: (i) What values did Ramesh demonstrate (any two values)? (ii) When does induced electromotive force arise? (iii) Name and state the law that gives the direction of induced current. [1+1+2=4] **OR** One morning, an old man was walking barefoot to replace the fuse wire of the kit-kat mains power supply in his house. Suddenly, he fell to the floor, screaming. His wife called for help. Anil, his neighbor's son heard the screams and, putting on his shoes, ran to the scene. He took a wooden baton and used it to turn off the mains power supply. Answer the following questions: (i) What is the voltage and frequency of the mains supply in India? (ii) For most of the electrical appliances we use today, we use AC voltage. Why? (iii) Write two qualities displayed by Anil in his activity. [1+1+2=4]

Aman was on his way to school. It had rained sometime ago. A color band was visible in the west. A question arose in his mind as to why a color band is visible. He discussed it with his classmates, but no one had a satisfactory answer. He put forth his problem to his teacher in the physics period. The teacher gave detailed information about the colour band. All the students were satisfied. Answer the following questions: (i) What two values did Aman demonstrate? (ii) Which two optical phenomena contribute to the formation of colour band? [2+2=4] **OR** Once while walking on the road, Ram saw a thin layer of oil lying in a water puddle. He noticed that beautiful colored stripes were visible on the surface when sunlight hit it. He was very impressed by this sight, but he was wondering how so many colors could be created from a single light. The next day, when wave optics was being discussed in class, he asked his teacher about this phenomenon. The teacher explained that this phenomenon occurs due to interference. When light reflected from the upper and lower surfaces of a thin layer meets each other, they undergo constructive interference at some places and destructive interference at others, creating many colored stripes. This is a beautiful example of the wavelike nature of light. Answer the following questions: (i) Explain constructive interference and destructive interference. (ii) What values do we get from this passage (any two values)? [2+2=4]

Write Ampere's circuital law, with the help of this law establish an expression for the intensity of the magnetic field inside the solenoid with the number of turns and flowing current. [1+4=5] **OR** Describe the moving coil galvanometer under the following points: (i) Labelled diagram (ii) Principle [2+3=5]

For concave spherical refracting surface prove that (μ−1)/R = μ/v − 1/u, where the symbols have their usual meanings. [5] **OR** Draw a ray diagram for compound microscope and derive an expression for magnifying power when— (i) final image is formed at least distance of distinct vision; (ii) final image is formed at infinity. [2+2+1=5]

Derive and write the Gauss's theorem. A point charge of 2.0 μC is placed at the centre of cubic Gaussian surface with 9 cm edge. Calculate net flux passing through the surface (ε₀ = 8.85×10⁻¹²). [3+2=5] **OR** What is capacitor? Explain its principle. Derive an expression for the capacitance of a parallel-plate capacitor. Write down two factors which affect the capacitance. [1+3+1=5]