Question
(a) Fig. 8.1 shows the magnetic field pattern around a bar magnet.
(i) Describe an experiment to identify the pattern and direction of magnetic field lines around
a bar magnet as shown in Fig. 8.1.
You may add to Fig. 8.1 as part of your answer.
(ii) State a material that can be used to make a permanent bar magnet.
(b) A student uses two bar magnets to create a uniform magnetic field. He places a current-
carrying wire at right angles to the magnetic field, as shown in Fig. 8.2.
There is a force on the current-carrying wire.
(i) The student wants to reverse the direction of the force on the wire.
State one change that reverses the direction of the force on the wire.
(ii) The student increases the separation of the poles of the permanent magnets.
State and explain how increasing the separation affects the force on the current-carrying
wire.
Answer/Explanation
Answer:
(a) (i) (plotting) compass OR iron filings
detail of method
use of (plotting) compass to give direction of field
(ii) steel
(b) (i) reverse magnetic field owtte OR reverse current in wire
(ii) force is weaker
(because) magnetic field is weaker
Question
Fig. 10.1 shows an arrangement for making an electromagnet.
(a) (i) State a material which is suitable for the core of the electromagnet.
(i) State the name for component X in Fig. 10.1.
(ii) Describe and explain how component X varies the strength of the electromagnet
(b) The switch is closed. The reading on the ammeter is 1.5 A.Calculate the resistance of the circuit.
resistance = ……………………………………………. Ω
Answer/Explanation
Answer:
(a)
(i) (soft) iron (bar)
(ii) variable resistor
(iii) any two from:
increasing the resistance
(will) decrease the current
(decreasing the current will) decrease the strength (of the electromagnet)
(b) (R=) V ÷ I in any form
(R=) 12 ÷ 1.5
(R=) 8.0 (Ω)