PHYSICS EXERCISE 3
1. (a)Draw and label a simple a.c dynamo.(b) Explain why an e.m.f is induced in the coil as it rotates.
(c) Show one of the positions of the coil when the dynamo produces maximum e.m.f.
(d) At what position of the coil is the induced e.m.f zero?
comment answer.
2. (a) Briefly explain the meaning of each of the following.
(i) Deviation
(ii) Dispersion
(iii) Pure spectrum
(b) Draw a ray diagram to illustrate how a pure spectrum of white light can be projected on a screen using two lenses and a prism.
(c) How does the colour of a body vary with the colour of the light in which it is viewed?
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Answer is ) (i) Deviation
(ii) Dispersion
(iii) Pure spectrum
(b) Draw a ray diagram to illustrate how a pure spectrum of white light can be projected on a screen using two lenses and a prism.
(c) How does the colour of a body vary with the colour of the light in which it is viewed?
comment answer.
3. (a) What is a hygrometer?
(b) A plastic tray weighing 48g and containing 200g of water at 20° is
put in a refrigerator which abstracts heat at a uniform rate of 21001/min. Calculate the
(i) Time is taken for the tray and water to reach 0°C
(ii) Total time is taken to freeze all the water to the ice at 0°C.
[Specific heat capacity of plastic = 1050J/kg K; specific latent heat of fusion of water = 335000J/kg]
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Answer is ) (b) A plastic tray weighing 48g and containing 200g of water at 20° is
put in a refrigerator which abstracts heat at a uniform rate of 21001/min. Calculate the
(i) Time is taken for the tray and water to reach 0°C
(ii) Total time is taken to freeze all the water to the ice at 0°C.
[Specific heat capacity of plastic = 1050J/kg K; specific latent heat of fusion of water = 335000J/kg]
comment answer.
4. (a) Define each of the following:
(i)Mechanical advantage.
(ii) Velocity ratio.
(b) A load of 50ON is raised through 5 metres by a machine when its effort E moves simultaneously through a distance of 25 metres along its direction. If the machine has an efficiency of 80%, calculate:
(i)Total work is done by the machine.
(ii) Value of E.
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Answer is ) (i)Mechanical advantage.
(ii) Velocity ratio.
(b) A load of 50ON is raised through 5 metres by a machine when its effort E moves simultaneously through a distance of 25 metres along its direction. If the machine has an efficiency of 80%, calculate:
(i)Total work is done by the machine.
(ii) Value of E.
comment answer.
5. (a) What are:
(i) Alpha particles (ii) Better particles (iii)Gamma rays.
(b) A radon nucleus Rn(222,86) emits an a-particle followed by å -particle.
What are the atomic number and mass number of the nucleus formed after the emission?
(c)A radioactive source has a half-life of 16 days. How long will it take for the count to fall from 160 per minute to 20 per minute?
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Answer is ) (b) A radon nucleus Rn(222,86) emits an a-particle followed by å -particle.
What are the atomic number and mass number of the nucleus formed after the emission?
(c)A radioactive source has a half-life of 16 days. How long will it take for the count to fall from 160 per minute to 20 per minute?
comment answer.
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