Question

an electric iron of resistance 20ohm takes a current of 5.A . calculate the heat developed on 0.5min.

Answer 1

here
r=20 ohms
i=5A
t=5×60=300s

we have formula
H=(i)^2 rt.
now put that value.
hope it helpful to u.

Answer 2

Resitance , R = 20 ohm
Current , I = 5 A
Time , t = 5 min. = 5 x 60 seconds = 300 sec.

Heat developed in 5 Minutes ,
H = I x I x R x t
= 5 x 5 x 20 x 300
= 25 x 20 x 300
= 500 x 300
= 150000 Joules