Verification of Joule’s Law using Joule’s Calorimeter - QS Study

Joule’s law is verified using Joule’s calorimeter. It consists of a resistance coil R enclosed inside a copper calorimeter (Figure).

Fig: Joule’s calorimeter

The ends of the coil are connected to two terminals, fixed to the lid of the calorimeter. A stirrer and a thermometer T are inserted through two holes in the lid. Two thirds of the volume of the calorimeter is filled with water. The calorimeter is enclosed in a wooden box to minimize loss of heat.

A battery (Bt), a key (K), a rheostat (Rh) and an ammeter (A) are connected in series with the calorimeter. A voltmeter (V) is connected across the ends of the coil R.

Verification of Joule’s Law

Law of resistance:

The same amount of current I is passed for the same time t through different coils of resistances R1, R2, R3 etc. The corresponding quantities of heat gained H1, H2, H3 etc. are calculated. It is found that,

H1/ R1 = H2/ R2 = H3/ R3

H/R = Constant

i.e H α R. Hence, law of resistance is verified.

Law of time:

The same amount of current I is passed through the same resistance R for different intervals of time t1, t2, t3 etc. The corresponding quantities of heat gained H1, H2, H3 etc. are calculated.

It is found that

H1/ t1 = H2/ t2 = H3/ t3

H/t = constant

i.e H α t. Hence, law of time is verified.