If the potential difference across the ends of a conductor is halved, what happens to the current flowing through it?
- A.It gets increased
- B.It gets doubled
- C.It gets decreased
- D.It gets halved
Correct answer
Explanation
The correct answer is D, it gets halved. By Ohm's law, at a constant temperature the current through a conductor is directly proportional to the potential difference across its ends, since the current equals the potential difference divided by the resistance. The resistance of the conductor does not change when the voltage is changed, so halving the potential difference halves the current exactly.
Option A is wrong because a smaller driving voltage cannot push a larger current through the same resistance. Option B is wrong for the same reason, and it describes what would happen if the voltage were doubled rather than halved. Option C, that the current gets decreased, is true as far as it goes but it is not the best answer, because the question can be answered exactly: the current does not merely fall, it falls to one half. In a question of this kind always give the precise proportional change rather than the vague direction of change.
Read the full article: Electricity and Magnetism: Laws, Rules and PYQs
Practice Questions
View allWhat is the work done to move a unit charge from one point to another in an electric circuit carrying some current, between those two points?
- A.Pressure distance
- B.Potential difference
- C.Potential distance
- D.Pressure difference
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The potential difference between two points in a circuit is defined as the work done in moving a unit positive charge from one point to the other.
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- B.Electric bulb (with filament)
- C.Electric iron
- D.Microwave
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Read the full explanation →A 12 V battery is connected across an unknown resistor. If a current of 2 mA is flowing through the circuit, the value of the resistance is _________ .
- A.600 ohm
- B.6 ohm
- C.6000 ohm
- D.60 ohm
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Read the full explanation →Thin wires of which of the following metal is used for making the filament of electric bulbs?
- A.Tungsten
- B.Silver
- C.Nichrome
- D.Copper
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Read the full explanation →The direction of the magnetic field produced around a straight current-carrying conductor is given by
- A.Fleming's left hand rule
- B.the right hand thumb rule
- C.Fleming's right hand rule
- D.Lenz's law
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