Please select a subject first
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Why is an electric light bulb not filled with air? Explain why argon or nitrogen is filled in an electric bulb.
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When a current of 4.0 A passes through a certain resistor for 10 minutes, 2.88 × 104 J of heat are produced. Calculate
the power of the resistor.
the voltage across the resistor.
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An electric heater of resistance 8 Ω takes a current of 15 A from the mains supply line. Calculate the rate at which heat is developed in the heater.
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Which of the following is the most likely temperature of the filament of an electric light bulb when it is working on the normal 220 V supply line?
(a) 500°C
(b) 1500°C
(c) 2500°C
(d) 4500°C
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In a filament type light bulb, most of the electric power consumed appears as:
(a) visible light
(b) infra-red-rays
(c) ultraviolet rays
(d) fluorescent light
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Calculate the resistance of an electric bulb which allows a 10 A current when connected to a 220 V power source.
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Define electric power. An electrical device of resistance R is connected across a source of voltage V and draws a current I. Derive an expression for power in terms of current and resistance.
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Unit of electric power may also be expressed as:
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The unit of e.m.f. of a cell is ____________.
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A cooler of 1500 W, 200 volts and a fan of 500 W, 200 volts are to be used from a household supply. The rating of fuse to be used is:
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Electric power is inversely proportional to ____________.
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What is the commercial unit of electrical energy?
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Compare the power used in the 2 Ω resistor in each of the following circuits:
- a 6 V battery in series with 1 Ω and 2 Ω resistors
- a 4 V battery in parallel with 12 Ω and 2 Ω resistors.
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What is the commercial unit of electrical energy? Represent it in terms of joules.
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What is the meaning of electric power of an electrical device? Write its SI unit.
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A student wants to use an electric heater, an electric bulb and an electric fan simultaneously.
How should these gadgets be connected with the mains? Justify your answer giving three reasons.
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