Unit: Electricity
Year: 1991 Question#: 31
Question: In the circuit diagram below, what is the potential difference across the 3.0-ohm resistor?
(1 ) 1.0 V
(2 ) 2.0 V
(3 ) 3.0V
(4 ) 1.5V
What is this question really asking?
Explanation by: Liz M.
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Answer 1
1.0 V
INCORRECT
You probably assumed that potential difference = R/V and plugged in the 3 ohms and 3 volts into that formula. This would give you an anwer of 1 which is incorrect. To answer this you need to look in the Ref. table under Parallel Circuits and see that
This will help you answer the question
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Answer 2
2.0 V
INCORRECT
You probably assumed that potential difference = R/V and you then preceeded to plug in 6 ohms for R and 3 ohms for V thus getting an answer of 2.0 V. This would be incorrect. To answer this you need to look in the Ref. table under Parallel Circuits and see that
This will help you answer the question
return to top Answer 3
3.0 V
CORRECT
You most like knew that potential difference reamins the same across all resistors when dealing with parallel circuits. So the amount of partial voltage traveling across the 3.0 ohm resistor must equal the total voltage. If you were unsure, you must have consulted the reference table and found the formula:
This can help you answer the question
return to top Answer 4
1.5V
INCORRECT
You probably assumed that the voltage would split in half when going through each resistor, but you neglected to recall the formula for resistance in a parallel circuit:
(this can be found in your reference table under parallel circuits) This formula
should help you realize that the voltage remains the same when going through each
resistor, so it must equal the total voltage (3.0V)
return to top What's this question really asking?
This question is asking if the student knows how to look up the parallel circuit formula in the Reference table. It is simply a case of plugging in the numbers. return to top
