The a.c. generator
4.5.2What the syllabus asks of you
- Describe a simple form of a.c. generator (rotating coil or rotating magnet) and the use of slip rings and brushes where needed
- Sketch and interpret graphs of e.m.f. against time for simple a.c. generators and relate the position of the generator coil to the peaks, troughs and zeros of the e.m.f.
Read the notes first
Chapter 4: The a.c. generator
Drill this topic
Every question on The a.c. generator, untimed, marked as you go.
Make a worksheet
Choose the years and how many questions, then print it with the answers on separate pages.
11 questions
1May / June 2025 · Paper 11 · Q32Show mark scheme →
A0° 90° 180°
B0° 90° 270°
C90° 180° 0°
D90° 270° 0°
Mark scheme
2May / June 2025 · Paper 12 · Q32Show mark scheme →
Agraph: e.m.f. rises from 0 at 0° to a maximum then falls back to 0 at 180°
Bgraph: e.m.f. starts at a maximum at 0° and decreases, crossing zero, becoming negative at 180°
Cgraph: e.m.f. sinusoidal, starting at 0, rising to a maximum, crossing zero, reaching a negative minimum, returning to 0 at 180°
Dgraph: e.m.f. decreases linearly from a maximum at 0° to zero at 180°
Mark scheme
3May / June 2024 · Paper 11 · Q34Show mark scheme →
AN pole; split-ring commutator
BN pole; slip rings
CS pole; split-ring commutator
DS pole; slip rings
Mark scheme
4Oct / Nov 2023 · Paper 11 · Q31Show mark scheme →
Agraph A: sinusoidal voltage output against time
Bgraph B: square wave voltage output against time
Cgraph C: sinusoidal voltage output against time
Dgraph D: triangular voltage output against time
Mark scheme
5Oct / Nov 2023 · Paper 12 · Q35Show mark scheme →
Adecreases, 1
Bdecreases, 4
Cdoes not change, 1
Ddoes not change, 4
Mark scheme
6Oct / Nov 2022 · Paper 11 · Q34Show mark scheme →
ADiagram A: sine wave with larger amplitude and same frequency as original
BDiagram B: sine wave with smaller amplitude and lower frequency
CDiagram C: sine wave with same amplitude and lower frequency
DDiagram D: sine wave with same amplitude and higher frequency
Mark scheme
7Oct / Nov 2022 · Paper 12 · Q35Show mark scheme →
Agraph A
Bgraph B
Cgraph C
Dgraph D
Mark scheme
8May / June 2021 · Paper 11 · Q35Show mark scheme →
A
B
C
D
Mark scheme
9Oct / Nov 2020 · Paper 12 · Q34Show mark scheme →
Aa battery
Ba coil of wire
Ca voltmeter
Da relay
Mark scheme
10May / June 2019 · Paper 12 · Q37Show mark scheme →
A[trace showing four full sine waves with same amplitude]
B[trace showing four full sine waves with larger amplitude]
C[trace showing one full sine wave with same amplitude]
D[trace showing one full sine wave with larger amplitude]
Mark scheme
11May / June 2018 · Paper 11 · Q33Show mark scheme →
Agraph of V against t showing full-wave rectified sine (all positive humps)
Bgraph of V against t showing half-wave rectified sine (positive humps separated by zero)
Cgraph of V against t showing constant zero voltage
Dgraph of V against t showing a continuous sinusoidal wave
Mark scheme