A hot plate of an electric oven connected to a 220 V line has two resistance coils A and B, each of 240 resistance, which may be used separately, in series, or in parallel. What are the currents in the three cases ?

Explanation

V= 220 V
R = 24 `Omega`
(i) When two coils are connected separately
`I = (V)/(R) = (220)/(24)= 9.2 A `
(ii) When two coils are connected in series
`R_(s)= 24 +24 = 48 Omega`
`I = (V)/(R_(s))= (220)/(48) = 4.6 A `
When two coils are connected in parallel, the resistance of the combination is
`(1)/(R_(p))=(1)/(24)+(1)/(24)=(1+1)/(24)=(2)/(24)=(1)/(12)`
`R_(p) = 12 Omega`
`I = (V)/(R_(p))=(220)/(12) = 18.3 A `