Question

1. An electric lamp of 100 12, a toaster of resistance 50 l, and a water
filter of resistance 500 12 are connected in parallel to a 220 V source.
What is the resistance of an electric iron connected to the same source
that takes as much current as all three appliances, and what is the
current through it?(ITQ)
​

Answer 1

Explanation:

(1) Total resistance (R) can be calculated as shown below.

1/R = 1/R₁ + 1/R₂ + 1/R₃

1/R = 1/100 + 1/50 + 1/500

1/R = ( 5 + 10 + 1 )/500

1/R = 16/500

500/16 = R

Total Resistance (R) = 500/16 Ω

R = 31.25 Ω

(2) According to ohm’s law the current through a conductor between two points is directly proportional to the voltage across the two points.

V ∝ I or V = IR

R is constant called resistance.

R = V/I

500/16 = 220/I

I = 220 × (16/500)

I = 7.04 A

Therefore, the resistance of the electric iron is 31.25 Ω and the current flowing through it is 7.04 A.