Question

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

Answer 1

Given: Voltage of power source (V) = 220 V

Resistance of coil A R₁ = 24 Ω

Resistance of coil B R₂ = 24 Ω

(a) In the first case - when these coils are connected to separate power sources, then

Current flowing I = `"V"/"R"_1 = "V"/"R"_2 = 220/24` = 9.2 A

Therefore, current flowing through each coil is 9.2 A

(b) In the second case - when they are connected in series, then the total resistance

R = R₁ + R₂

= 24 Ω + 24 Ω

= 48 Ω

Therefore, the flowing electric current I = `"V"/"R"`

= `(220 "V")/(48 Ω)`

= 4.58 A

= 4.6 A

(c) In the third case – when the coils are connected in parallel, then the total resistance is,

`1/"R" = 1/"R"_1 + 1/"R"_2`

= `1/24 + 1/24`

= `2/24`

R = `24/2` = 12 Ω

Hence the flowing electric current I = `"V"/"R"`

= `(220 "V")/(12 Ω)`

= 18.33 A

= 18.3 A