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SAI International School
Class VII
Lesson Notes
Subject: Physics
Ch- Electric current and simple circuit
Subtopic: Heating effects of Current

Effects of Electric current:

The energy stored in electric current is called Electrical energy.
The electrical energy is converted into different forms of energy like heat energy, mechanical
energy, etc. It can produce different effects of electric current.
Current can be calculated by

Current =

SI unit of current is Ampere (A).
Heating effect of electric current:
When electric current passes through a conductor, electrical energy is converted into heat
energy. This is known as heating effects of electric current.
The heat produced by the conducting wire depends upon
I. The amount of resistance offered by the wire, that is, more is the resistance, more heat is
produced.
II. Cross-sectional area of the wire.
III. Amount of current passing through the wire.
IV. Amount of time current passing through the wire.

Advantages of tungsten over copper to be used as filament of the bulb:
Copper wire generally has very low resistance and does not get heated quickly, but a thin
wire of tungsten heats up quickly as it has high resistance and starts to glow. This is the
reason for which tungsten is preferred over copper to be used as filament of the bulb.

REASONS FOR THE USE OF NICHROME WIRE AS A HEATING ELEMENT IN
ELECTRICAL APPLIANCES:
(i) It is a good conductor of heat.
(ii) It offers high resistance, so a lot of heat is generated.
(iii) It has high melting point.
(iv) It does not oxidize easily.

COMPARISION OF CFL WITH AN ELECTRIC BULB:
(i) CFL reduces wastage of electricity by producing less heat and more light.
(ii) CFL lasts longer than incandescent bulbs.