A wire of length 1 m is available. The battery has zero internal resistance. In which of the following arrangements is the energy (power) drawn from the battery the greatest?

The wire is cut into four equal parts connected in parallel across the battery.
The full length of the wire is connected across the battery.
Half the length of the wire is connected across the battery.
The wire is cut into two equal parts connected in parallel across the battery.

Correct answer: The wire is cut into four equal parts connected in parallel across the battery.

Solution

Resistance of the full wire is R. Four equal parts in parallel give R/16, the smallest resistance, hence the largest power V²/R drawn.

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