A cell is arranged in series with an ammeter and a variable resistor. A voltmeter is used to measure the p.d. across the variable resistor. The resistance of the variable resistor is changed, and the p.d. and current are noted. The graph shows how the p.d. across the variable resistor varies with current. What is the internal resistance of the cell?
- A$0.050\,\Omega$
- B$1.6\,\Omega$
- C$20\,\Omega$
- D$23\,\Omega$