Unit: Electricity and magnetism
Year: 1994 Question#: 33
Question: The diagram below shows a circuit with two resistors.
Compared to the potential drop across the 8-ohm resistor, the potential drop across the 4-ohm resistor is
(1 ) the same
(2 ) twice as great
(3 ) one-half as great
(4 ) four times as great
What is this question really asking?
Explanation by: Dana H
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Answer 1
the same
Incorrect, If they were the same they would each have to be equal to each resistances. return to top
Answer 2
twice as great
Incorrect, 4 ohms is 1/2 as great as 8 ohms. return to top
Answer 3
one-half as great
Correct, 4-ohms creates 1/2 the resistance of 8 ohms. So using Ohm's law, V=IR we find that if R is smaller we get a smaller voltage drop across the resistor. return to top
Answer 4
four times as great
Incorrect, in order to be four times as great the 4 ohm resistor would actually have to be 32 ohms. return to top
What's this question really asking?
How does the potential drop across resistances work in a series circuit? return to top
