How should the student change the circuit to give negative values for current and potential difference?

Reversing the polarity of the battery reverses the polarity in the circuit.

Explanation:

In a DC circuit, the polarity of the potential difference and the current is determined by the polarity of the battery or the power source.

Reversing the polarity of the battery reverses the polarity in the circuit.

In the case of current, the direction of the movement of the electrons is reversed and in the case of the potential difference, this is measured with respect to a minimum fly in general taken as zero.

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photocells convert light energy to electricity