1 \begin{problem*}{Q19.13} % internal resistance
2 Explain in detail how you could measure the internal resistance of a
11 MultiTerminal B = source(type=DC, label="$V$");
12 MultiTerminal r = resistor(B.terminal[1], type=normal, label="$r$");
13 MultiTerminal R = resistor((0,u), type=normal, label="$R$");
14 MultiTerminal I = current((r.terminal[1].x, R.terminal[1].y), dir=180,
15 label=Label("$I$", align=N));
16 wire(B.terminal[0], R.terminal[0], udsq);
17 wire(r.terminal[1], I.terminal[0], udsq);
18 wire(I.terminal[1], R.terminal[1], nsq);
21 Make a circuit using a known resistance $R$ to connect the two
22 terminals of the battery, and measure the current $I$.
24 From Kirchhoff's loop rule
28 r &= \ans{\frac{V}{I} - R}