Case: Read the following passage and answer accordingly.
The current through a single resistor R across which there is a potential difference V is given by Ohm’s law \( I=V/R \). Resistors are sometimes joined together and there are simple rules for the calculation of equivalent resistance of such a combination. Two resistors are said to be in series if only one of their endpoints is joined. Two or more resistors are said to be in parallel if one end of all the resistors is joined together and similarly the other ends joined together.
Which of the following quantities is the same across resistors when they are connected in parallel?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Voltage
Option (1) Current — Incorrect. The current divides among the branches. Each branch carries \( V/R \), so different resistors carry different currents.
Option (2) Power — Incorrect. Each resistor dissipates \( V^2/R \), which is different for different resistances.
Option (3) Voltage — Correct. In a parallel combination, one end of every resistor is joined to one point. The other ends are joined to another common point. So each resistor is connected between the same two points. Hence the potential difference across each resistor is the same, while the current divides as \( I=V/R \).
Option (4) Both current and voltage — Incorrect. Only the voltage is common. The currents \( V/R \) in the branches differ unless all the resistances are equal.