More Questions from Resistance and Power

Core relationship in Ohm’s law Which statement correctly describes the proportionality between current and resistance when the applied voltage is held constant?

Electronics Resistance and Power Difficulty: Easy
Choose an option
  • A
    current is inversely proportional to resistance
  • B
    resistance is directly proportional to voltage
  • C
    voltage is indirectly proportional to power
  • D
    current is directly proportional to resistance

Answer

Correct Answer: current is inversely proportional to resistance

Explanation

Introduction / Context:Ohm’s law is the cornerstone of basic circuit analysis. It defines a simple linear relationship among voltage, current, and resistance, allowing quick predictions of how one variable changes when another is adjusted.

Given Data / Assumptions:

  • Ohmic components and linear operating region.
  • Applied voltage is constant.
  • Temperature and material properties assumed stable.

Concept / Approach:Ohm’s law: V = I * R. Solving for current yields I = V / R. With V fixed, it is clear that current varies inversely with resistance: doubling R halves I; halving R doubles I. This inverse proportionality is fundamental to resistor networks and load-line analysis.

Step-by-Step Solution:Start from V = I * R.Hold V constant and isolate I: I = V / R.Observe: I is proportional to 1/R.Therefore, current is inversely proportional to resistance at constant voltage.

Verification / Alternative check:Plot I versus R for fixed V: a rectangular hyperbola passing through (R, I) pairs such as (1 kΩ, 10 mA) and (2 kΩ, 5 mA).

Why Other Options Are Wrong:Resistance directly proportional to voltage: not a general law; R is material/geometry dependent.Voltage indirectly proportional to power: mixing relationships; power depends on both V and I.Current directly proportional to resistance: contradicts I = V / R.

Common Pitfalls:Ignoring temperature dependence in real resistors; at high power, R may change, but the law’s proportionality at a given instant still applies.

Final Answer:current is inversely proportional to resistance

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