For a hypothetical electronic device, the potential difference V in volts, measured across the device, is related to the current i in mA by . (a) We have to find the resistance when the current is . (b) We have to find the value of the current when the resistance is equal to .

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Important point to note in answering this problem is to distinguish between the Ohm’s law and the definition of the resistance. Resistance of a circuit element, R, is defined to be the ratio of the potential difference across the element, V, and the current, i, flowing through it. That is

Relation between the potential difference V and the current i in a hypothetical electronic device is given to be

where the current i is measured in mA. Therefore,

Therefore, for

Resistance offered by the element will be when the current is