Question

State joule's law of heating . List applications of joule's heating effect in daily life.(3mark)

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Answer 1

(a) Joule's law of heating states that power of heating generated by an electrical conductor is proportional to the product of its resistance (R) and square of the electric current passing through the conductor with time. Heat generated (W) = I2Rt. Electric bulbs are usually filled with argon or Krypton.

(b) Four applications of Joule's heating effect in daily life are:

(i) Electric fuse is a safety circuit devices work on this principle.

(ii) Electric iron we use to iron our clothes works on this principle.

(iii) Electric kettle used to boil water also works on this principle.

(iv) Electric toaster to make bake breads works on the same principle.

Answer 2

According to Joule's law of heating, if heat H is being produced in a wire then:

⠀⠀⠀⠀⠀⠀⠀⠀⠀H∝I²

⠀⠀⠀⠀⠀⠀⠀⠀⠀H∝R

⠀⠀⠀⠀⠀⠀⠀⠀⠀H∝t

where I is current in wire R is resistance of wire and t is the for which current flows.

Combining all factors.

Heat produced in a wire is given by H=I²Rt in Joule

> Applications of Joule's heating effect in daily life :

(1) The heating effect of current is utilised in the working of electric heating appliances such as electric iron, electric kettle, electric toaster, electric oven, room heaters, geysers, etc.

(2) The heating effect of electric current is utilised in electric bulbs.

(3) The heating effect of electric current is utilised in electric fuse for protecting household wiring and electrical appliances