Question 22N.2.HL.TZ0.5
| Date | November 2022 | Marks available | [Maximum mark: 9] | Reference code | 22N.2.HL.TZ0.5 |
| Level | HL | Paper | 2 | Time zone | TZ0 |
| Command term | Calculate, Explain, Identify, Show that, State | Question number | 5 | 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.
One of the connecting wires is placed in a magnetic field. The direction of the current in the wire is shown.
State what is meant by an ideal voltmeter.
[1]
infinite resistance
OR
no current is flowing through it ✓
A majority of candidates scored a mark by simply stating infinite resistance. Several answers went the other way round, stating a resistance of zero.
Calculate, in mA, the current in the resistor.
[1]
«mA» ✓
Very well answered, with most candidates successfully answering in the required unit of 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.
Calculate the emf of the cell.
[2]
139 × 10−3 (10.0 + 0.73)
OR
29.4 × 10−3 (50.0 + 0.73) ✓
1.49 «V» ✓
Watch for ECF from 5(b)(i).
Usually well answered, regardless of b(ii), by utilising the show that value given.
Explain, by reference to charge carriers in the wire, how the magnetic force on the wire arises.
[2]
charge/carriers are moving in a magnetic field ✓
there is a magnetic force on them / quote F = qvB
OR
this creates a magnetic field that interacts with the external magnetic field ✓
Accept electrons.
For MP2, the force must be identified as acting on charge / carriers.
Many scored MP1 here but did not get MP2 as they jumped straight to the wire rather than continuing with the explanation of what was going on with the charge carriers.
Identify the direction of the magnetic force on the wire.
[1]
into the plane «of the paper» ✓
Generally, a well answered question although there was some confusion on how to communicate it, with some contradictory answers indicating into or out, and also North or South at the same time.