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How do the input and output powers in a transformer compare? State the assumption made.
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Define the term kilowatt-hour and state its value in S.I unit
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The temperature of the surrounding starts falling when ice in a frozen lake starts melting. Give reason.
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Give two differences between the radioactive decay and nuclear fission.
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What do you mean by power rating of an electrical appliance? How do you use it to calculate the resistance of the appliance.
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What do you mean by power rating of an electrical appliance? How do you use it to calculate the safe limit of current in it, while in use?
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An electrical appliance has a rating 100 W, 120 V. The resistance of element of appliance when in use is ______.
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State one advantage of using a total reflecting prism as a reflector in place of plane mirror.
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Explain the meaning of the statement 'the power of an appliance is 100 W'.
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An electrical appliance having a resistance of 200 Ω is operated at 200 V. Calculate the energy consumed by the appliance in 5 minutes in joules.
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'A geyser is rated 240 W-220 V'. Explain the meaning of this statement.
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Draw a diagram of a right angled isosceles prism which is used to make an inverted image erect.
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State and define the household unit of electricity.
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What is the voltage of the electricity that is generally supplied to a house?
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Two lamps, one rated 220 V, 50 W and the other rated 220 V, 100 W, are connected in series with mains of 220 V. Explain why does the 50 W lamp consume more power.
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What is the resistance, under normal working conditions, of an electric lamp rated at '240 v, 60 W' ? If two such lamps are connected in series across a 240 V mains supply, explain why each one appears less bright.
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Two bulbs are rated 60 W, 220 V and 60 W, 110 V respectively. Calculate the ratio of their resistances.
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Sumit does 600 J of work in 10 min and Amit does 300 J of work in 20 min. Calculate the ratio of the powers delivered by them.
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Three heaters each rated 250 W, 100 V are connected in parallel to a 100 V supply. Calculate:
- the total current taken from the supply
- the resistance of each heater and
- the energy supplied in kWh to the three heaters in 5 hours.
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A ball is placed on a compressed spring. What form of energy does the spring possess? On releasing the spring, the ball flies away. Give a reason.
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