Two light bulbs are connected in parallel to a 6.0 V battery. Each bulb has a resistance of 10 Ω. What is the total resistance of the circuit?

Two light bulbs are connected in parallel to a 6.0 V battery. Each bulb has a resistance of 10 Ω. What is the total resistance of the circuit?

• A. 3 Ω
• B. 5 Ω
• C. 6 Ω
• D. 10 Ω

Answer: (B)

In a parallel circuit, the total resistance is found by adding the reciprocals of each branch’s resistance. For two identical resistors of 10 Ω, 1/R_total = 1/10 + 1/10 = 2/10 = 1/5, so R_total = 5 Ω. This value is smaller than either resistor because making multiple paths for current lowers the overall opposition to current flow. The battery provides 6.0 V, so the circuit current would be I = V/R_total = 6/5 = 1.2 A. Therefore, the total resistance of the circuit is 5 Ω.

In a parallel circuit, the total resistance is found by adding the reciprocals of each branch’s resistance. For two identical resistors of 10 Ω, 1/R_total = 1/10 + 1/10 = 2/10 = 1/5, so R_total = 5 Ω. This value is smaller than either resistor because making multiple paths for current lowers the overall opposition to current flow. The battery provides 6.0 V, so the circuit current would be I = V/R_total = 6/5 = 1.2 A. Therefore, the total resistance of the circuit is 5 Ω.