Paper 2 · November 2016 · Current-voltage characteristic of an electronic device (diode)
The current-voltage graph of an electronic device shows negligible current until about 2 V, then a steep, non-linear rise in current as voltage increases further. Which statement best describes the resistance of this device?
AThe resistance is not constant; it decreases as the voltage (and current) increases.
BThe resistance is constant at all voltages, since the device obeys Ohm's law and current stays directly proportional to voltage.
CThe resistance increases steadily as the voltage increases, the same way it would for a simple fixed resistor.
DThe resistance is zero at all voltages above 2 V, because conduction becomes essentially unrestricted once it starts.
Explanation
Because the current rises non-linearly with voltage, the device does not obey Ohm's law; its resistance decreases as voltage and current increase.
Derived from ZIMSEC Physics 5055/2 Paper 2 Theory, November 2016, Q7