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Kristin Fracchia

ACT Challenge Question 19: Ohm’s Law – Answer and Explanation

Magoosh ACT Challenge Question


Were you able to solve the ACT Challenge Question we posted on Monday? If you missed it, check it out here, then scroll down below for the answer.

ACT Challenge Question 19

Does the information provided in the passage and Table 1 support the conclusion that as voltage increases in a circuit, current always increases?

A. Yes, circuits with the highest voltage always produced the highest current.

B. Yes, circuits with the lowest resistance always produced the highest current.

C. No, circuits with highest resistance produced the lowest current.

D. No, circuits with the highest voltage produced the highest current only when the resistance was held constant.

Answer and Explanation

The answer is D.

Don’t be fooled by answer choice A!  Referring to Table 1, we find the relationship described by the question stem. Notice that the resistance is held constant throughout. Only answer choice D correctly describes the situation—current only increases if the resistance is held constant. In other words, if a much higher resistance value were used in a circuit with a higher voltage battery, we couldn’t necessarily conclude that the current would be higher without knowing that the resistance was held constant in our comparison. You can also figure this out by looking at the equation for Ohm’s law: V = I x R. If the resistance is held constant then we can see there is a directly proportional relationship between voltage and current. But if the resistance were to change it would affect the entire equation.


About Kristin Fracchia

Kristin makes sure Magoosh's blogs are chock-full of awesome, free resources for students preparing for standardized tests. With a PhD from UC Irvine and degrees in Education and English, she’s been working in education since 2004 and has helped students prepare for standardized tests, as well as college and graduate school admissions, since 2007. She enjoys the agonizing bliss of marathon running, backpacking, hot yoga, and esoteric knowledge.

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