Question 22N.2.HL.TZ0.5b.ii
| Date | November 2022 | Marks available | [Maximum mark: 2] | Reference code | 22N.2.HL.TZ0.5b.ii |
| Level | HL | Paper | 2 | Time zone | TZ0 |
| Command term | Show that | Question number | b.ii | Adapted from | N/A |
Resistor R is connected in a circuit with a cell that has internal resistance.
The ammeter and the voltmeter are ideal.
The resistance of R is 50.0 Ω. The voltmeter reads 1.47 V.
Resistor R is replaced by another of resistance 10.0 Ω. The ammeter now reads 139 mA.
Show that the internal resistance of the cell is about 0.7 Ω.
[2]
29.4 (50.0 + r) = 139 (10.0 + r) ✓
attempt to solve for r, e.g. 29.4 × 50.0 − 139 × 10.0 = r (139 − 29.4)
OR
0.73 «Ω» ✓
Do not allow working backwards from 0.7 Ω.
Many answers here produced a number that did not round to 0.7 but students claimed it did. The simultaneous equation approach was seen in the best candidates, getting the right answer. It is worthy of reminding about the need of showing one more decimal place when calculating a show that value type of question.
