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प्रश्न
Why is the heating element of an electric oven wound on a helix? State the reason.
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उत्तर
In an electric oven, the china clay plate is provided either with lateral grooves or grooves in the form of a spiral helix. This type of spiral winding reduces the area of spread of nichrome wire and helps to concentrate heat in a small region.
संबंधित प्रश्न
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
When a current I flows through a resistance R for time t, the electrical energy spent is given by:
(a) IRt (b) I²Rt (c) `IR^2t` (d) `I^2R ⁄t`
An electric bulb is rated ‘100 W, 250 V’. How much current will the bulb draw if connected to a 250 V supply?
An electric iron rated 750 W is operated for 2 hours/day. How much energy is consumed by the electric iron for 30 days?
State other bigger units of electric power and express them in watt.
The equation I2R seems to suggest that the rate of heating in a resistor is reduced if resistance decreases, whereas equation P = V2/R suggests just the opposite. How do you reconcile this problem?
A bulb is marked 100W, 220V and an electric heater is marked 2000 W, 220 V.
(i) What is the ratio between the resistances of these two devices?
(ii) How does the power-voltage rating of a device help us to decide about the type of leads (connecting wires) to be used for it?
(iii) In which of the above two devices, a thicker connecting wire of lead is required?
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.
