What is the definition of electric potential difference (p.d.)?
The way the current $I$ in a semiconductor diode varies with potential difference $V$ is shown in Fig. 6.1. Use Fig. 6.1 to describe qualitatively how the diode’s resistance changes as $V$ rises from $0$ to $1.0\,\text{V}$.
The diode in part (b) forms part of the circuit in Fig. 6.2. The cell has electromotive force (e.m.f.) $2.0\,\text{V}$ and negligible internal resistance, and it is connected in series with the diode and resistors X and Y. Resistor Y has resistance $60\,\Omega$. The current in the cell is $15\,\text{mA}$. (i) Use Fig. 6.1 to find the resistance of the diode. (ii) Calculate: 1. the resistance of X 2. the ratio $\dfrac{\text{power dissipated in resistor Y}}{\text{total power produced by the cell}}$.