An electric iron of resistance 20 Ω takes a current of 5 A

Question 3:

An electric iron of resistance 20 Ω takes a current of 5 A. Calculate the heat developed in 30 s.

Solution:

Given that Resistance(R) = 20 Ω, Electric current (I)= 5 A and time(t)= 30 s

Now we know that H= I²Rt

                                = 5×5×20×30

                                = 15000J=1.5×10⁴J

∴ The heat developed in 30s is 1.5×10⁴J