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CIE iGCSE Co-Ordinated Science P4.5.4 Force on a current-carrying conductor Exam Style Questions Paper 2

CIE iGCSE Co-Ordinated Science Paper 2 - All Chapters

Question

The diagram shows the direction of the current in a wire. The wire is placed between the poles of a magnet and this causes a force to act on the wire.

In which labelled direction does the force act?

▶️ Answer/Explanation
Using Fleming’s left-hand rule (thumb = force, first finger = magnetic field, second finger = current), the force direction is perpendicular to both. From the diagram, the correct direction is labelled B. Hence answer B.
✅ Answer: (B)

Question

A current-carrying conductor is in a magnetic field. This causes a force to act on the conductor.

The current is increased and the magnetic field is reversed.

Which statement describes the force after the changes to the current and the magnetic field?

A. The force is greater and in the opposite direction.
B. The force is greater and in the same direction.
C. The force is the same and in the same direction.
D. The force is the same and in the opposite direction.

▶️ Answer/Explanation
The force on a current-carrying conductor in a magnetic field is given by \(F = BIL\), where \(B\) is magnetic field strength, \(I\) is current, and \(L\) is the length of the conductor. When the current is increased, the force becomes greater. When the magnetic field is reversed, the direction of the force reverses (since force is perpendicular to both current and magnetic field). Therefore, the force is greater and in the opposite direction.
✅ Answer: (A)

Question

A current-carrying wire is placed between the poles P and Q of a magnet, as shown.

The direction of the current is shown.

A force acts on the wire upwards, as shown.

What is the direction of the magnetic field?

A. from P to Q
B. from Q to P
C. towards the bottom of the page
D. towards the top of the page

▶️ Answer/Explanation
Using Fleming’s left-hand rule, with the thumb (force) pointing up and the second finger (current) in the given direction, the First finger (field) must point from P to Q.
This orientation of the three mutually perpendicular directions is what produces an upward force on the wire.
✅ Answer: (A)

Question

The diagram shows a current-carrying conductor in a magnetic field. The direction of the current is shown.

In which direction is the force on the wire due to the magnetic field?

A. downwards
B. to the left
C. to the right
D. upwards

▶️ Answer/Explanation
Using Fleming’s left-hand rule, with the field running from the North to the South pole and the current direction as shown, the thumb (force direction) points downwards.
This is the motor effect: the wire experiences a mechanical force perpendicular to both the current and the magnetic field.
✅ Answer: (A)

Question

The diagram shows a wire carrying a current, lying in a magnetic field between two magnetic poles (N on the left, S on the right). The arrow on the wire shows the direction of the current.

What is the direction of the magnetic field and what is the direction of the force on the wire?

▶️ Answer/Explanation
Magnetic field lines run from the north pole to the south pole, so with N on the left, the field points to the right.
Using the given current direction together with the field direction and applying the left-hand (motor) rule for force, field and current.
This combination produces a resultant force acting downwards on the wire.
✅ Answer: (C)
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