If you double the resistance of one branch in parallel, what happens to that branch's current?

If you double the resistance of one branch in parallel, what happens to that branch's current?

• A. It doubles
• B. It halves
• C. It remains the same
• D. It goes to zero

Answer: (B)

In a parallel circuit, the voltage across each branch is the same, and the branch current follows I = V/R. If you double the resistance of one branch while the supply voltage stays fixed, that branch’s current becomes I' = V/(2R) = (1/2)(V/R). So the current in that branch is halved. The other branches see the same voltage and are unaffected by this change in the first branch, though the total current drawn from the source would decrease accordingly.

In a parallel circuit, the voltage across each branch is the same, and the branch current follows I = V/R. If you double the resistance of one branch while the supply voltage stays fixed, that branch’s current becomes I' = V/(2R) = (1/2)(V/R). So the current in that branch is halved. The other branches see the same voltage and are unaffected by this change in the first branch, though the total current drawn from the source would decrease accordingly.