Electric current is used to generate heat by ‘ heating element’ based electric appliances like- heater, electric bulb, hair dryer, immersion rod for heating water, toaster, electric press, glue gun, hair straighter, electric tea kettles, electric girdle, clothes dryers, fridge defrostrator etc. All these appliances work on principle of heating effect of current. The amount of heat produced by an electric appliance depend upon-amount of current, resistance of conductor or poor conductor and duration of current flow.
H (Heat Produced) = I2.R.t
Here, I- represents current
R- represents resistance
And t –represents time
In honour of James Prescott Joule, the S.I unit of energy, heat and work is called Joule (J).
|
S.N. |
HEATING ELEMENT |
CONCERNED ELECTRIC APPLIANCE |
|
1 |
Tungsten metal |
Electric Bulb |
|
2 |
Nichrome wire (Alloy of 80 % Nickel and 20 % Chromium) |
Electric heater |
|
3 |
Nichrome wire |
Electric press |
|
4 |
Mica Sheet |
Hair dryer, Electric press and toaster |
Q.1.1What is the S.I. Unit of heat and energy?
(a) Watt (b) Calorie (c) Joule (d) Kilo joule
Q.1.2 What are the factors responsible generation of heat by electric appliances?
A. Amount of Current B. Resistance of heating element
C. Body of the electric appliance D. Electric switch
Options- (a) Both A and C (b) Both A and B
(c) Both C and D (D) Both A and D
Q.1.3 ‘Star Ratings’ and ‘I.S.I. mark’ on electric appliances are their credibility of being good. Why are they indicated on such appliances?
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Q.1.4 If the amount of current passing in the electric appliance is increased, what will be the effect on heat production?
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