Question

(a) State and explain Joule's law of heating.
(b) A resistance of 40 ohms and one of 60 ohms are arranged in series across 220 volt supply. Find the heat in joules produced by this combination of resistances in half a minute.

Answer 1

Explanation:

(b) Let R1 = 40 ohm

R2 = 60 ohm

A/c to question ,

R1 and R2 are in series combination,

so, equivalent Resistance (Req) = R1 + R2

Req = 40 + 60 = 100 ohm

now ,

we know ,

Heat = I²Rt

also , V = IR ( according to ohm' s law )

Heat = (V/R)² ×R × t

= V²× t/R

here,

Req = R = 100 ohm

V = 220 volt

t = 30 sec

then,

Heat = (220)² × 30/100 Joule

= 48400 × 30/100 Joule

= 484 × 30 Joule

= 14520 Joule

hence, heat = 14520 Joule

Answer 2

Explanation:

hope it's help you......