Final answer:
The relationship between potential difference and current in a copper wire at constant temperature is directly proportional, as described by Ohm's Law (I = V/R). A graph representing this relationship would be a straight line passing through the origin.
Step-by-step explanation:
The relationship between the potential difference applied to a copper wire and the resulting current in the wire at a constant temperature is directly proportional. This relationship is described by Ohm's Law, which states that the current (I) flowing through a conductor is equal to the potential difference (V) applied across it divided by the resistance (R) of the conductor: I = V/R.
Therefore, when the potential difference applied to a copper wire is increased, the resulting current flowing through the wire also increases, and vice versa. A graph representing this relationship would be a straight line passing through the origin (0,0).