In a circuit with a fixed resistance, the voltage drop across the resistor depends on which quantity?

• A. Amperage of the circuit
• B. Resistance of the conductor
• C. The voltage of the circuit
• D. The temperature

Answer: (A)

Understanding how voltage drop across a fixed resistor relates to current.

Ohm’s law, V = I R, governs this. When the resistance is fixed, the voltage drop across that resistor scales directly with the current flowing through it. Doubling the current doubles the voltage drop for the same resistance. For example, a 5-ohm resistor with 0.5 A current drops 2.5 V, and with 1 A, it drops 5 V. The resistance value sets the proportionality, but the actual drop depends on how much current is flowing. Temperature effects or changes in the overall supply can affect current or resistance, but with the resistance held constant, the direct determinant of the drop is the current.