What potential difference is required to cause 4.00 A to flow through a resistance of 330 ohm?

Ohm's Law: Voltage = current times resistance

4 amperes times 330 ohms = 1320 volts

However, this represents a power of 5280 watts, and the resistor will get very, very hot. As a result, temperature coefficient will enter into the equation, and the resulting resistance will probably be higher than expected.