Direct Ohm’s law implication — for a fixed-value resistor, if the voltage applied across it increases, how does the current through it change (assuming temperature effects are negligible)?

Difficulty: Easy

Correct Answer: Increases

Explanation:


Introduction / Context:
Ohm’s law gives an immediate relationship between the voltage across a resistor and the current through it. Understanding this proportionality is fundamental to predicting how changes in supply voltage affect branch currents in simple and complex circuits alike.


Given Data / Assumptions:

  • Resistor value R is constant and positive.
  • Temperature and self-heating effects are negligible for the change considered.
  • Polarity is fixed; we are discussing magnitude changes.


Concept / Approach:
Ohm’s law states V = I * R. Holding R constant implies I = V / R. Therefore, if V increases, I must increase proportionally. This is the definition of a linear, ohmic element. The exact numeric change requires R, but the qualitative direction (increase) does not.


Step-by-Step Solution:

Start from I = V / R for a fixed R.Consider a higher applied V: numerator increases while denominator is unchanged.Therefore I increases linearly with V.Conclude that current increases when voltage increases across a fixed resistor.


Verification / Alternative check:
Plot I vs. V: the line I = (1/R) * V has positive slope 1/R. Any movement to the right along the V-axis moves up along the I-axis.


Why Other Options Are Wrong:

  • Decreases/Stays the same: Contradicts I = V / R for constant R.
  • Cannot be determined: While the exact value needs R, the trend is determined.
  • Reverses direction: Direction is set by polarity; magnitude increase does not flip direction.


Common Pitfalls:
Confusing constant-current sources (which enforce I) with resistors (which follow Ohm’s law); ignoring that significant heating can change R slightly, but the ideal law remains linear.


Final Answer:
Increases

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