Question

The above circuit is a part of an electrical device. Use the information given in the question to calculate the following.

1. Potential Difference across R₂.
2. Value of the resistance R₂.
3. Value of resistance R₁.

Answer 1

1. Potential difference across 4 Ω resistor = Potential Difference across R₂ as both are in parallel.
   = 1.5 (A) × 4 (Ω)
   = 6 V
2. Total Current through 4 Ω and R₂ = 2.0 A  ....(given)
   Current through 4 Ω = 1.5 A  ...(given)
   Hence current through R₂ = 2 − 1.5 = 0.5 A
   Using Ohm’s law for R₂, we get
   6 V = 0.5 A × R₂
   Hence R₂ = `6/0.5` = 12 Ω
3. Potential difference across R₁ = Total Potential difference − (Potential difference across R₂) − (Potential difference across 2.0 Ω)
   Potential difference across 2.0 Ω = 2 × 2 = 4 V
   Potential difference across R₂ = 6 V  ....(calculated before)
   Hence Potential difference across R₁ = 12 − 6 − 4 = 2 V
   Current through R₁ = 2A
   Using Ohm’s Law, we get
   R₁ = `(2V)/(2A)` = 1 Ω