AQA GCSE Combined Science: Trilogy · 6.7

Magnetism and electromagnetism

50 revision questions with answers for 6.7 Magnetism and electromagnetism in AQA GCSE Combined Science: Trilogy (spec 8464). Practise with flashcards, a topic quiz, a random quiz across the course, 5 crosswords, or read every question and answer below.

All 50 questions and answers

Question 1 · Spec 6.7.1.1
Where are a bar magnet's magnetic forces strongest?
Answer:
At its poles.
Question 2 · Spec 6.7.1.1
What happens when two like magnetic poles approach?
Answer:
They repel each other.
Question 3 · Spec 6.7.1.1
What happens when two unlike magnetic poles approach?
Answer:
They attract each other.
Question 4 · Spec 6.7.1.1
Why are magnetic attraction and repulsion non-contact forces?
Answer:
They act across a gap without the objects physically touching.
Question 5 · Spec 6.7.1.1
What is a permanent magnet?
Answer:
A magnet that produces its own persistent magnetic field.
Question 6 · Spec 6.7.1.1
What is an induced magnet?
Answer:
A material that becomes magnetised when placed in an external magnetic field.
Question 7 · Spec 6.7.1.1
Why is unmagnetised iron attracted to either pole of a magnet?
Answer:
The field induces an opposite pole in the nearer end of the iron, producing attraction.
Question 8 · Spec 6.7.1.1
What usually happens when an induced magnet leaves the external field?
Answer:
It quickly loses most or all of its induced magnetism.
Question 9 · Spec 6.7.1.2
Name four magnetic materials in the specification.
Answer:
Iron, steel, cobalt and nickel.
Question 10 · Spec 6.7.1.2
What is a magnetic field?
Answer:
The region around a magnet where a force acts on another magnet or a magnetic material.
Question 11 · Spec 6.7.1.2
How is the direction of a magnetic field defined?
Answer:
The direction of force on a north pole placed at that point.
Question 12 · Spec 6.7.1.2
Which way do field lines point outside a bar magnet?
Answer:
From the north pole towards the south pole.
Question 13 · Spec 6.7.1.2
How does a bar magnet's field strength usually change with distance?
Answer:
It becomes weaker farther from the magnet.
Question 14 · Spec 6.7.1.2
What does close field-line spacing represent?
Answer:
A stronger magnetic field; more widely spaced lines represent a weaker field.
Question 15 · Spec 6.7.1.2
Why can a compass indicate magnetic field direction?
Answer:
Its magnetised needle turns to align with the local field; the north-seeking end indicates the field direction.
Question 16 · Spec 6.7.1.2
What does compass behaviour suggest about the Earth?
Answer:
The Earth has a magnetic field, providing evidence for magnetic effects associated with its core.
Question 17 · Spec 6.7.1.2
How can a plotting compass map a bar magnet's field?
Answer:
Mark needle directions at successive points, join them into curves and add arrows; repeat from different starting points.
Question 18 · Spec 6.7.1.2
What can iron filings show, and what do they not show directly?
Answer:
They reveal the field's pattern, but not its direction; a compass is needed to add direction arrows.
Question 19 · Spec 6.7.1.1
An object is attracted to a magnet. Does that prove it is a permanent magnet?
Answer:
No. An unmagnetised magnetic material can also be attracted through induced magnetism.
Question 20 · Spec 6.7.1.1
Why is repulsion a stronger test for an object's permanent magnetism than attraction?
Answer:
Repulsion requires like magnetic poles, whereas attraction can occur with an unmagnetised magnetic material.
Question 21 · Spec 6.7.2.1
What happens around a wire when current flows through it?
Answer:
A magnetic field is produced around the wire.
Question 22 · Spec 6.7.2.1
What is the field pattern around a straight current-carrying wire?
Answer:
Concentric circles centred on the wire, in planes perpendicular to it.
Question 23 · Spec 6.7.2.1
How does the right-hand grip rule give a straight wire's field direction?
Answer:
Point the right thumb in the conventional-current direction; curled fingers show the magnetic field direction.
Question 24 · Spec 6.7.2.1
How does increasing current affect a wire's magnetic field?
Answer:
It increases the magnetic field strength at a fixed distance.
Question 25 · Spec 6.7.2.1
How does increasing distance from a current-carrying wire affect field strength?
Answer:
The magnetic field becomes weaker.
Question 26 · Spec 6.7.2.1
What happens to a wire's magnetic field when current direction reverses?
Answer:
The field direction reverses.
Question 27 · Spec 6.7.2.1
How can a compass demonstrate the magnetic effect of current?
Answer:
Place it near a wire; switching current on deflects the needle, and reversing current reverses the deflection.
Question 28 · Spec 6.7.2.1
What is a solenoid?
Answer:
A coil of wire that produces a magnetic field when current flows through it.
Question 29 · Spec 6.7.2.1
Describe the field inside a long solenoid.
Answer:
It is strong and approximately uniform, shown by straight, parallel, equally spaced field lines.
Question 30 · Spec 6.7.2.1
How does a solenoid's external field compare with a bar magnet's?
Answer:
It has a similar pattern, with a north pole at one end and a south pole at the other.
Question 31 · Spec 6.7.2.1
How can an iron core change a solenoid's field?
Answer:
It becomes magnetised and increases the overall field strength, forming an electromagnet.
Question 32 · Spec 6.7.2.1
Why does coiling a wire increase its magnetic effect?
Answer:
Fields from neighbouring turns combine, producing a stronger field inside the coil.
Question 33 · Spec 6.7.2.1
Why can an electromagnet be switched on and off?
Answer:
Its magnetic field depends on current; switching off removes the current-produced field and most induced core magnetism.
Question 34 · Spec 6.7.2.1
How can a solenoid's north and south ends be swapped?
Answer:
Reverse the current through the coil.
Question 35 · Spec 6.7.2.1
Why is an electromagnet useful on a crane that moves iron scrap?
Answer:
It attracts the scrap when current flows and can release it when the current is switched off.
Question 36 · Spec 6.7.2.2 · Higher only
What is the motor effect?
Answer:
A current-carrying conductor in a magnetic field experiences a force; it also exerts an opposite force on the magnet.
Question 37 · Spec 6.7.2.2 · Higher only
How is motor-effect force directed relative to current and field?
Answer:
It is perpendicular to both the conventional current and the magnetic field.
Question 38 · Spec 6.7.2.2 · Higher only
State Fleming's left-hand rule finger meanings.
Answer:
First finger: magnetic field; second finger: conventional current; thumb: force or motion. Hold the three at right angles.
Question 39 · Spec 6.7.2.2 · Higher only
What happens to force if current reverses while field stays the same?
Answer:
The force reverses direction.
Question 40 · Spec 6.7.2.2 · Higher only
What happens to force if magnetic field reverses while current stays the same?
Answer:
The force reverses direction.
Question 41 · Spec 6.7.2.2 · Higher only
What happens to force direction if both current and field reverse?
Answer:
It remains the same, because the two reversals cancel.
Question 42 · Spec 6.7.2.2 · Higher only
When is the force on a straight current-carrying wire zero because of its orientation?
Answer:
When the wire and current are parallel to the magnetic field.
Question 43 · Spec 6.7.2.2 · Higher only
State the motor-effect force equation and its condition.
Answer:
F = BIl, for a straight conductor at right angles to the magnetic field.
Question 44 · Spec 6.7.2.2 · Higher only
Give units for B, I and l in F = BIl.
Answer:
Magnetic flux density B: tesla, T; current I: amperes, A; active conductor length l: metres, m.
Question 45 · Spec 6.7.2.2 · Higher only
Find force for B = 0.40 T, I = 3.0 A and l = 0.20 m at right angles.
Answer:
F = 0.40 × 3.0 × 0.20 = 0.24 N.
Question 46 · Spec 6.7.2.2 · Higher only
How does force change if current doubles at fixed B and perpendicular length?
Answer:
It doubles, because force is directly proportional to current.
Question 47 · Spec 6.7.2.2 · Higher only
Why use only the wire length inside the field in F = BIl?
Answer:
Only that active length experiences the stated magnetic field; wire outside it does not contribute the same force.
Question 48 · Spec 6.7.2.3 · Higher only
Why can a current-carrying coil rotate in a magnetic field?
Answer:
Opposite sides experience forces in opposite directions, producing a turning effect.
Question 49 · Spec 6.7.2.3 · Higher only
Why are forces on opposite coil sides in opposite directions?
Answer:
Current flows in opposite directions along those sides while the magnetic field direction is the same.
Question 50 · Spec 6.7.2.3 · Higher only
What is the useful energy transfer in an electric motor?
Answer:
Energy is transferred electrically to mechanical work and the kinetic store of moving parts, with some dissipation to thermal stores.

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