CAIE IGCSE Physics 5.2.1.4 Count rate measured in counts/s or
Practise using count rate units correctly, converting detector readings into counts/s or counts/minute for radiation measurements.
- Syllabus
- 2026–2028
- Course
- Physics 0625
Practise using count rate units correctly, converting detector readings into counts/s or counts/minute for radiation measurements.
Fig. 10.2 shows an electric door lock.
The slot in the door contains an unmagnetised iron bolt attached to a spring.
The slot in the door frame is empty. This slot is surrounded by the coils of a solenoid.
In Fig. 10.2 the door is unlocked. The spring is not stretched.

Fig. 10.2
In Fig. 10.3 the door is locked. The spring is now stretched.

Fig. 10.3
The bolt is initially in the position shown in Fig. 10.2.
Describe and explain what happens when
the switch S is closed,
any four from these six:
- charge flows OR current in solenoid / wire / circuit
- solenoid becomes magnet / magnetised
- bolt becomes magnet / magnetised
- (such that) unlike poles (of solenoid and bolt are) facing o.w.t.t.e.
- bolt is attracted
- bolt moves / (door) locks / spring stretched
B4
the switch S is reopened.
solenoid OR bolt no longer magnetised OR bolt no longer attracted
B1
(spring contracts and pulls) bolt back / bolt returns (to original position) / (door) unlocked
B1