Difficulty: Easy
Correct Answer: one 220 Ω resistor
Explanation:
Introduction / Context:
Total power drawn from a constant-voltage source depends on the equivalent resistance. This question checks your understanding of how power changes when series resistance increases while the supply voltage is held constant.
Given Data / Assumptions:
Concept / Approach:
For a fixed voltage source, total power P_total equals V^2 / R_total. Therefore, smaller R_total yields larger P_total. In series, resistances add: R_total = n * 220 Ω, where n is the number of resistors in series.
Step-by-Step Solution:
Verification / Alternative check:
Numerical example: P_1 = 120^2 / 220 ≈ 65.45 W; P_2 ≈ 32.73 W; P_3 ≈ 24.55 W; P_4 ≈ 16.36 W. The trend confirms the reasoning.
Why Other Options Are Wrong:
Adding more resistors increases R_total and therefore reduces total power drawn from the same source voltage.
Common Pitfalls:
Confusing constant-current with constant-voltage cases; incorrectly averaging resistances instead of summing for series.
Final Answer:
one 220 Ω resistor
Discussion & Comments