A researcher investigates how the electric current passing through a new tungsten-carbide heating element varies with the potential difference across it.
State the equation linking potential difference (voltage), current, and resistance.
Calculate the resistance of the heating element when the potential difference is 15.0 V15.0\text{ V}15.0 V. Show your working and state the unit.
The researcher reverses the connections to the power supply. Describe the shape of the graph that would be obtained for negative voltages.
