# An Electric Heater Which is Connected to a 220 V Supply Line Has Two Resistance Coils A And B Of 24 ω Resistance Each. These Coils Can Be Used Separately (One at a Time), in Series Or in Parallel. Calculate the Current Drawn When: (A) Only One Coil A Is Used. (B) Coils A And B Are Used in Series. (C) Coils A And B Are Uses in Parallel. - Science

An electric heater which is connected to a 220 V supply line has two resistance coils A and B of 24 Ω resistance each. These coils can be used separately (one at a time), in series or in parallel. Calculate the current drawn when:

(a) only one coil A is used.
(b) coils and B are used in series.
(c) coils and B are uses in parallel.

#### Solution

(a) When only one coil, A is used:
V = IR
220 = 24 I
I = 9.2 A

(b) When coils, A and B are used in series:
Total resistance RARB = 48 Ω
V = IR
220 = 48 I
I = 4.58 A

(c) When coils, A and B are used in parallel:
1/= 1/RA+ 1/RB
Here, R= 24 Ω and RB = 24 Ω
1/R = 1/24 + 1/24
or 1/= 2/24
= 12 Ω
Total resistance of parallel combination, R = 12 Ω
Now, V = IR
220 = 12 I
I = 18.33 A

Concept: System of Resistors - Resistances in Parallel
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