Question 4
FA long straight wire passes vertically through a hole in a horizontal sheet of card. The current in the wire is upwards.
Three plotting compasses, W, X and Z, are placed on the card.
The Figure shows the apparatus.
Figure
a.[1]
Describe the shape of the magnetic field lines around the wire.
b.[1]
State whether the field lines go clockwise or anticlockwise when viewed from above the card.
c.[1]
The needles of compasses W and X point in opposite directions.
Explain why.
d.[1]
The needle of compass Z is deflected much less than the needles of compasses W and X.
Explain why.
e.[2]
The current is switched off.
Describe and explain what happens to all three compass needles.
4.1 Magnets and magnetic fields Questions
44 exam-style questions on OCR GCSE Physics 4.1 Magnets and magnetic fields, covering 4.1.1 Magnetic poles, attraction and repulsion, 4.1.2 Permanent and induced magnets, 4.1.3 The magnetic field of a magnet, 4.1.4 Compasses and the Earth's magnetic field, 4.1.5 The magnetic field around a current-carrying wire, 4.1.6 Field strength, current and distance, and 4.1.7 Solenoids and electromagnets. Each one has a worked solution and a mark scheme showing where the marks go.