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Question
If the voltage across a fixed resistance is doubled, what happens to the current?
  1. It doubles.
  2. It halves.
  3. It stays the same.
  4. The current cannot be determine
Question by OpenStax is licensed under CC BY 4.0.
Final Answer

(a)

Solution Video

OpenStax College Physics for AP® Courses Solution, Chapter 20, Problem 5 (Test Prep for AP® Courses) (0:50)

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Video Transcript

This is College Physics Answers with Shaun Dychko. Ohm's Law says voltage equals current times resistance and so we can solve this for current by dividing both sides by <i>R</i>. So we have in the first case in the first circuit, we have current one equals the voltage one divided by <i>R</i> and I did not put a subscript on the <i>R</i> because we're told that the resistance is fixed, so it's the same for both circuits. Now in circuit two, we have the voltage two divided by the same resistance <i>R</i>. But <i>V two</i> we're told is double <i>V one</i> and so I've substituted two <i>V one</i> in place of <i>V two</i>. Now we see that this part is <i>I one</i> and so <i>I two</i> is two times <i>I one</i>. So the answer is A, it doubles.