Question

Fig. 12.1 shows a wire being moved between the poles of a magnet.
The wire is connected to an ammeter which measures the current induced in the wire as the wire
is moved. When the wire moves from left to right the ammeter shows a positive reading.

(a) (i) Explain why a current is induced in the wire as it is moved between the poles of the magnet.

(ii) Place ticks (3) in Table 12.1 to show how the reading on the ammeter changes under different conditions.

(b) A magnet is used to investigate the behaviour of ionising radiation.
(i) Fig. 12.2 shows the paths taken by three types of ionising radiation as they pass through a magnetic field.

The path taken by an alpha particle has been labelled for you.
State the types of radiation which would follow the paths labelled P and Q.

P …………………………………………………………………………
Q …………………………………………………………………………

(ii) When americium‐241 (²⁴¹ ₉₅Am) decays it emits an alpha particle.

Use the correct nuclide notation to complete the decay equation for americium‐241.

(iii) Americium‐241 is a source of alpha particles. It is used in smoke detectors.
Fig. 12.3 shows part of the inside of a smoke detector. The alpha particles cause a current in the sensor.

When the detector fills with smoke, a change in current is detected by a sensor which sounds an alarm.

Suggest two reasons why a source of alpha particles is used and not any other type of ionising radiation.
1 …………………………………………………………………………
2 …………………………………………………………………………

▶️Answer/Explanation

Ans : 12(a)(i) the wire experiences a changing magnetic field ;

an emf is induced in the wire ;

12(a)(ii) 

12(b)(i) (P:) beta AND
(Q:) gamma ;

12(b)(ii) 

12(b)(iii) least penetrating / short range ;
easily stopped by smoke ;
AVP ;