Copper wire of certain length and resistance is drawn out to three times its length without change in volume, the new resistance of wire becomes__________?
Correct answer: C. 9 times
- A. 1/9 times
- B. 3 times
- C. 9 times
- D. unchanged
Explanation
With constant volume, making the wire three times longer makes its cross-sectional area one-third as large. Since R = ρL/A, the resistance changes by 3 ÷ (1/3) = 9, giving nine times the original value.
Report an error
The more specific you are, the faster it gets fixed. A source beats an opinion.
Prefer email? [email protected]
Practise Circuit Analysis
394 free Circuit Analysis MCQs from Electrical Engineering, each with the correct answer and an explanation. Unlimited attempts, no account needed.
Discussion
Stuck on an option, or know a faster way to get there? Ask or explain it here.
No comments yet. Be the first to explain this one.
Exams that ask Electrical Engineering questions like this
Electrical Engineering is on 2 papers prepared for on TestUstad, and all of them draw the same bank, so this question is worth knowing for every one of them.
More Circuit Analysis questions
When resistance element of a heater fuses and then we reconnect it after removing a portion of it, the power of the heater will___________?
Three identical resistors are first connected in parallel and then in series. The resultant resistance of the first combination to the second will be_________________?
Three 6 ohm resistors are connected to form a triangle. What is the resistance between any two corners ___________?
74. Sparking occurs when a load is switched off because the circuit has high_________?
In the case of direct current____________?
Two lamps 100 W and 40 W are connected in series across 230 V (alternating). Which of the following statement is correct ?