What happens to the current in the series circuit if the resistance is doubled?

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Examoogle · Accepted Answer

It becomes half its original value

Explanation: According to Ohm's Law, the current $I$ flowing through a circuit is inversely proportional to the resistance $R$ for a constant applied voltage $V$. Therefore, if the resistance is doubled ($R' = 2R$) while the voltage remains constant, the new current $I'$ becomes half of the original current.

Working Principle: The relationship is governed by the equation $I = \frac{V}{R}$. When $R$ is changed to $2R$, the new current $I'$ is calculated as $I' = \frac{V}{2R} = \frac{1}{2} 	imes (\frac{V}{R}) = \frac{I}{2}$. This demonstrates the fundamental inverse linear relationship between resistance and current in a purely resistive DC circuit.

Key Formulas: $I = \frac{V}{R}$ — Ohm's Law relating Current, Voltage, and Resistance; $I' = \frac{V}{2R} = \frac{1}{2}I$ — Effect of doubling resistance on current

Key Points: Ohm's law holds true for linear resistive elements.; Current is inversely proportional to resistance when voltage is constant.; Increasing resistance restricts the flow of charge carriers.; The power dissipation $P = I^2R$ would also decrease if resistance were increased while maintaining constant voltage.

Advantages: Simple linear relationship for analysis; Predictable circuit behavior

Disadvantages: Assumes constant temperature (resistance changes with heating)

Applications: Current limiting in LED circuits; Voltage divider networks; Basic circuit troubleshooting

Additional Info: The result assumes the source voltage remains perfectly constant (an ideal voltage source).. Option B is incorrect as it describes direct proportionality, which is false for resistance.. Options C and D represent extreme limits (R=0 or R=infinity) which do not occur by simply doubling the value.

Answer: A is correct — The current becomes half its original value because current is inversely proportional to resistance in a circuit with constant voltage.

Exam Tip: Always verify if the voltage source is defined as constant before assuming inverse proportionality between $I$ and $R$.

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