A hot plate of an electric oven connected to a `220 V` lines has two resistance coils `A and B`, each of `24 Omega` resistance, which may be used separately, in series or in parallel. What are the currents in the three cases ?

Options

A. 10.2 A, 20 A, 19 A
B. 9.2 A, 4.6 A, 18.3 A
C. 7.4 A, 50 A, 29 A
D. None of these

Answer

B

Explanation

Here, potential difference, `V = 220 V`
resistance of each coil, `r = 24 Omega`
(i) When each of the coils `A or B` is connected separately, current through each coil, i.e.,
`I = (V)/( r) = (220 V)/(24 Omega) = 9.2 A`
(ii) When coils `A and B` are connected in series, equivalent resistance in the circuit,
`R_s = r + r = 2r = 48 Omega`
Current through the series combination, i.e., `I_s = (V)/(R_s)=(220 V)/(48 Omega) = 4.6 A`
(iii) When the coils `A and B` are connected in parallel, equivalent resistance in the circuit,
`R_p = ( r)/(2) = (24 Omega)/(2) = 12 Omega`
Current through the parallel combination, i.e., `I_p = (V)/(R_p) = (220 V)/(12 Omega) = 18.3 A`.