HSC Science (Electronics) १२ वीं कक्षा - Maharashtra State Board Question Bank Solutions for Physics

Calculate the average molecular kinetic energy 

1. per kmol 
2. per kg 
3. per molecule 

of oxygen at 127°C, given that the molecular weight of oxygen is 32, R is 8.31 J mol⁻¹K⁻¹ and Avogadro’s number N_A is 6.02 × 10²³ molecules mol⁻¹.

Energy is emitted from a hole in an electric furnace at the rate of 20 W when the temperature of the furnace is 727°C. What is the area of the hole? (Take Stefan’s constant σ to be 5.7 × 10^-8 Js^-1 m^-2K^-4.)

The emissive power of a sphere of area 0.02 m² is 0.5 kcal s^-1m^-2. What is the amount of heat radiated by the spherical surface in 20 seconds?

Compare the rates of emission of heat by a blackbody maintained at 727°C and at 227°C, if the black bodies are surrounded by an enclosure (black) at 27°C. What would be the ratio of their rates of loss of heat?

Earth’s mean temperature can be assumed to be 280 K. How will the curve of blackbody radiation look like for this temperature? Find out λ_max. In which part of the electromagnetic spectrum, does this value lie? (Take Wien's constant b = 2.897 × 10⁻³ m K)

Find the temperature of a blackbody if its spectrum has a peak at (a) λ_max = 700 nm (visible), (b) λ_max = 3 cm (microwave region) (c) λ_max = 3 m (short radio waves). (Take Wien’s constant b = 2.897 × 10^-3 m.K).

An ideal monoatomic gas is adiabatically compressed so that its final temperature is twice its initial temperature. What is the ratio of the final pressure to its initial pressure?

Answer in brief.

Using differential equations of linear S.H.M, obtain the expression for (a) velocity in S.H.M., (b) acceleration in S.H.M.

Find the change in length of a second’s pendulum, if the acceleration due to gravity at the place changes from 9.75 m/s² to 9.8 m/s².

Answer in brief.

For a stationary wave set up in a string having both ends fixed, what is the ratio of the fundamental frequency to the second harmonic?

Derive an expression for the equation of stationary wave on a stretched string.

Find the amplitude of the resultant wave produced due to interference of two waves given as y₁ = A₁ sinωt, y₂ = A₂ sin(ωt + φ)

Describe how a potentiometer is used to compare the emf's of two cells by the combination method.

Why is a potentiometer preferred over a voltmeter for measuring emf?

A standing wave is produced in a tube open at both ends. The fundamental frequency is 300 Hz. What is the length of the tube? (speed of the sound = 340 m s^-1).

The resistance of a potentiometer wire is 8 Ω and its length is 8 m. A resistance box and a 2 V battery are connected in series with iL What should be the resistance in the box if it is desired to have a potential drop of 1 µV/mm?

When two cells of emf's E₁ and E₂ are connected in series so as to assist each other, their balancing length on a potentiometer wire is found to be 2.7 m. When the cells are connected in series so as to oppose each other, the balancing length is found to be 0.3 m. Compare the emf's of the two cells.

The emf of a cell is balanced by a length of 120 cm of a potentiometer wire. When the cell is shunted by a resistance of 10 Ω, the balancing length is reduced by 20 cm. Find the internal resistance of the cell.

A piece of straight wire has mass 20 g and length 1 m. It is to be levitated using a current of 1 A flowing through it and a perpendicular magnetic field B in a horizontal direction. What must be the magnitude B of the magnetic field?

An aircraft of wing span of 50 m flies horizontally in the Earth's magnetic field of 6 x 10^-5 T at a speed of 400 m/s. Calculate the emf generated between the tips of the wings of the aircraft.