State and derive joule’s law. An electric iron consumes energy at rate of 420w when heating is at maximum rate and 180 w when heating is at minimum. The voltage is 220V .What is the current and resistant in each case?
(i) When heating is maximum, the power P1 = 420 W Applied voltage V = 220 V P = VI Current I = P V PV I = 420 220 420220 = 1.909 A I = 1.909 A (ii) When heating is minimum Power P2 = 180 W Applied voltage V = 220 V P = VI ∴ Current I = P V PV I = 180 220 180220 = 0.8181 A I = 0.8181
