Question

A lamp of resistance 20 Ω is joined to a battery of 12 V. Find the value of the resistance to be connected in series with the lamp in order to get current of 0.5 A.​

Answer 1

Given :

• Voltage, V = 12 V
• Current, I = 0.5 A
• Resistance of the lamp, R₁ = 20 Ω

Need to find :

• Resistance to be connected, R₂

Solution :

★ Using ohm's law,

• R = V/I

→ R = 12/0.5

→ R = 24 Ω

But, R = R₁ + R₂

∴ 24 = 20 + R₂

∴ R₂ = 4 Ω

• Hence, the resistance to be connected is 4 Ω.