Three resistors are connected in parallel to the voltage source with resistors R1 = 30 Ω, R2 = 150 Ω and R3 = 90 Ω. A current of 200 mA flows through the resistor R3. How much current flows through the resistor R1? The current is expressed in mA

0.6 A

Explanation:

When resistors are connected in parallel,

(i) The voltage across each of the resistor is the same

(ii) The current in the circuit is equal to the sum of the current flowing through the individual resistor.

Firstly, we look for the voltage across the the R₃ resistor.

From Ohm's law,

V₃ = I₃R₃ ... Equation 1

Where V₃ = Voltage across R₃, I₃ = current flowing through R₃

Given: I₃ = 200 mA = 0.2 A, R₃ = 90 Ω

Substitute into equation 1

V₃ = 0.2 (90) = 18 V.

Note: V₁ = V₃ = 18 V.

Secondly, we calculate the current flowing through R₁

Using,

I₁ = V₁/R₁ ... Equation 2

Given: V₁ = 18 V, R₁ = 30 Ω

Substitute these values into equation 2

I₁ = 18/30

I₁ = 0.6 A