If a wire of length L and diameter d has a resistance R, then another wire of the same material but having length four times and twice the diameter has the resistance:
Correct answer: B. Same as the first wire
- A. Half of the first wire
- B. Same as the first wire
- C. Twice of the first wire
- D. Four times of the first wire
Explanation
If the length of the wire is four times and the diameter is twice, then the length becomes 4L and the diameter becomes 2d. The cross-sectional area of the wire is proportional to the square of the diameter, so the area becomes (2d)2 = 4(d2). The resistance is inversely proportional to the area, so the resistance becomes R/(4(d2)). This is the same as the resistance of the first wire (R), so option B is correct.
Report an error
The more specific you are, the faster it gets fixed. A source beats an opinion.
Prefer email? [email protected]
About Current Electricity
Steady current relates charge flow to potential difference, resistance and resistivity, including how temperature changes a conductor's resistance. Sources with internal resistance have terminal voltage below their emf when delivering current, and maximum power output occurs under a specific load condition rather than at zero resistance.
Practise Current Electricity
1,052 free Current Electricity MCQs from Physics, 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 Physics questions like this
Physics is on 16 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 Current Electricity questions
If four different resistors are used to pass electric current for different time durations, then which of the following will produce the largest heating effect in joules?
In bringing an electron towards another electron, the electrostatic potential energy of the system will
If a wire is moulded in the form of a ring of radius r which encloses a charge q, then the strength of the electric field at the centre of the ring will be
If an electric iron of 120 ohms operates at 220 V, then the rate of heat developed is equal to:
In the given circuit diagram, the direction of the conventional current is from:
A 50 Ampere-hour battery can supply a current of 50 A for 1 hour, 25 A for 2 hour, and so on. Then the total energy stored in the 12V-50 Ampere-hour battery is: