CAIE IGCSE Physics 4.5.3.5 Effect on the magnetic field around

Practise predicting how changing current size or direction changes magnetic fields around straight wires, coils and solenoids.

Exam points

predict that increasing current makes the magnetic field stronger and field lines closer together
state that reversing the current reverses the magnetic field direction around a wire or solenoid

[Maximum number: 2]

Fig. 7.1 shows a barrier at the entrance to a car park. The wooden barrier arm has a weight of 60 N which acts through the centre of gravity at the position shown on Fig. 7.1.

Fig. 7.1

Fig. 7.2 shows a coil attached to a power supply placed below the soft iron bar A.

Fig. 7.2

The switch is opened. An operator decreases the potential difference across the coil and the switch is closed.

State and explain how the effect on the wooden barrier arm compares with the effect in (b)(i).
statement
explanation

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4.5.3.5—Effect on the magnetic field around question 1