Physics – Important Question Bank for Gujarat (12th std) HSC Board Exam 2020

PHYSICS – IMPORTANT QUESTION BANK

1. Write Kirchhoff’s First Law and obtain equation using necessary figure.
2. Indian style of cooling drinking water is to keep it in a pitcher having porous walls. Water comes to the outer surface very slowly and evaporates. Most of energy needed for evaporation is taken from the water itself and the water is cooled down. Assume that a pitcher contains 10 kg of water and 0.2 g of water comes out per second. Assuming no backward heat transfer from the atmosphere to the water, calculate the time in which the temperature decreases by 5°C. Specific heat capacity of water = 4200 J kg⁻¹°C⁻¹ and latent heat of vaporization of water = 2.27 × 10⁶ J kg⁻¹.
3. Depth of a well is 5.5 m and it is completely filled with water. The refractive index of water is 1.33. If viewed from the top, by how much height would the bottom of the well appear to be shifted up?
4. Calculate the principal quantum number for which the radius of the orbit of the electron: n be+³ would be equal to that for the ground state of electron in a Hydrogen atom and compare the energy of the two states.
5. When a linear object is placed in front of a convex mirror, image of the 1/4 the size of object is formed. Calculate the object distance and the image distance. This linear object is kept perpendicular to the axis.
6. A glass window is to be fit in an aluminum frame. The temperature on the working day is 40°C and the glass window measures exactly 20 cm × 30 cm. What should be the size of the aluminum frame so that there is no stress on the glass in winter even if the temperature drops to 0°C? Coefficients of linear expansion for glass and aluminum are 9.0 × 10^–6°C^–1 and 24 ×100^–6°C^–1, respectively.
7. Give first hypothesis of Bohr model and using it, derive expression for radius of the orbit of electron in Hydrogen atom.
8. A drop of water (spherically shaped) has 3 x 10-10 C amount of charge residing on it. 500 V electric potential exists on its surface. Calculate the radius of this drop. Two such drops (having identical charge and radius) combine to form a new drop. Calculate the electric potential on the surface of the new drop. K = 9 x 109 SI.
9. Explain half – wave rectifier with necessary circuit and graphs.
10. A gas thermometer measures the temperature from the variation of pressure of a sample of gas. If the pressure measured at the melting point of lead is 2.20 times the pressure measured at the triple point of water, find the melting point of lead.
11. Draw Input and Output characteristics for CE transistor circuit. Write the formula for input resistance (ri) and output resistance (ro).
12. Explain charging process in Lead storage cell (accumulator), using necessary circuit.
13. An electric bulb of volume 250 cc was sealed during manufacturing at a pressure of 10⁻³mm of mercury at 27°C. Compute the number of air molecules contained in the bulb. Avogadro constant = 6 × 10²³ mol⁻¹, density of mercury = 13600 kg m⁻³ and g = 10 m s⁻².
14. Write the differential equation for L-C oscillations obtain its solution and show that charge on capacitor and current through inductor changes periodically.
15. A circular coil having N turns is made from a wire of L meter length. If a current of I amp. is passed through the coil, which is suspended in a uniform magnetic field of B Tesla, find the maximum torque that can act on the coil.

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16. Write limitations of Bohr model.
17. A vessel contains 1.60 g of oxygen and 2.80 g of nitrogen. The temperature is maintained at 300 K and the volume of the vessel is 0.166 m³. Find the pressure of the mixture.
18. Write down points of comparison between an electric dipole and a magnetic dipole.
19. A railway track (made of iron) is laid in winter when the average temperature is 18°C. The track consists of sections of 12.0 m placed one after the other. How much gap should be left between two such sections, so that there is no compression during summer when the maximum temperature rises to 48°C? Coefficient of linear expansion of iron = 11 × 10^–6°C¹.
20. Explain charging process in Lead storage cell (accumulator), using necessary circuit.
21. The collector current changes by 5 mA whe4the input voltage of the NPN common emitter amplifier changes by 2 00 mV The A. C. current gain of this circuit is equal to I00.1f we have to obtain a power gain of 5 000 then what should be the value of the load resistance?
22. The geostationary orbit of the earth is at a distance of about 36000 km from the earth’s surface. Find the weight of a 120-kg equipment placed in a geostationary satellite. The radius of the earth is 6400 km.
23. The width of slit of 0.0I2mm monochromatic light is incident on it. The angular position of first bright line is J.2’Find the wave-length of incident light.
24. Give Einstein’s explanation for Photoelectric effect.
25. A circular coil having N turns is made from a wire of L meter length. If a current of I amp. is passed through the coil, which is suspended in a uniform magnetic field of B Tesla, find the maximum torque that can act on the coil.
26. Write four uses of a Photocell.
27. What is Power Factor? Explain experimental arrangement of Hertz experiment with necessary diagram and show that it forms an oscillator circuit.
28. 10% of the total energy of a 100 W bulb is converted into visible light. Calculate the average intensity at a spherical surface which is at a distance of 2 m. from the bulb. Consider the bulb to be a point source and let the medium be isotropic.
29. Height of TV tower is 102 M. If the average population density is 1000 / km2, how many people can observe the programmes of this station? (Radius of the Earth = 6400 km)
30. Explain Analog communication, Digital communication, Simple communication and Duplex communication.

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31. Write uses of LASER Light.
32. A patient has been given a dose of radioactive material. When a counter is brought near him it records 20,000 counts per minute. Under similar conditions the same counter records 625 counts per minute after a lapse of 5 hours. Find the half life of the radioactive material.
33. Two long solenoids are of equal length 1 and the smaller solenoid having a cross sectional area a is placed within the larger solenoid in such a way that their axes coincide. Find the mutual inductance of the system.
34. The pressures of the gas in a constant volume gas thermometer are 80 cm, 90 cm and 100 cm of mercury at the ice point, the steam point and in a heated wax bath, respectively. Find the temperature of the wax bath.
35. A real image formed by a concave mirror is four times the object size. If object is taken 3 cm away, the image is 3 times enlarged. Calculate the focal length of the mirror.