Question

a resistance of 40 ohms and 60 ohms are arranged in series across 220 volt supply. find the heat in joules produced by this combination in half a minute

Answer 1

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

Hi friend,
As resistances are connected in series equivalent resistance will be sum of given resistances =60+40=100Ω
Current flowing through circuit is=V/R=220/100=2.2 amperes
Time (t)=30 seconds
Heat generated (H)=i²Rt
i=2.2A,R=100Ω,time=30s
H=(2.2)²(30)(100)
  =14520 joules.