Magnetic Fields

What Magnetic Fields covers

Magnetic Fields is examined in Component 3, Light, Nuclei and Options, Section A, which every student sits. It covers the motor effect and Fleming's left-hand rule, F = BIl sinθ and measuring magnetic flux density, the force on a moving charge, F = Bqv sinθ, the Hall effect and the Hall probe, magnetic fields due to a straight wire and a solenoid, forces between current-carrying conductors and charged particle beams and accelerators.

The 7 subtopics

Each one has its own page.

• The motor effect and Fleming's left-hand ruleMotor effect, fleming's left-hand rule and why a simple d.Open →
• F = BIl sinθ and measuring magnetic flux densityRecall questions on the equation with every symbol, why only the length inside the field counts, the effect of the angle, the current balance experiment and what is plotted, what the gradient gives, and worked force and flux density calculations.Open →
• The force on a moving charge, F = Bqv sinθRecall questions on the equation and why a stationary charge feels no force, its derivation from F = BIl, why the magnetic force does no work, the circular path that results with r = mv/Bq, and the period being independent of speed.Open →
• The Hall effect and the Hall probeHall effect and steps by which a Hall voltage builds up.Open →
• Magnetic fields due to a straight wire and a solenoidRecall questions on the shape and direction of the field around a straight wire and inside a solenoid, the right-hand grip rule for each, B = μ₀I/2πa and B = μ₀nI with every symbol, the permeability of free space, and worked field calculations.Open →
• Forces between current-carrying conductorsRecall questions on why two parallel currents attract or repel depending on their directions, the force per unit length equation, how the definition of the ampere follows from it, and worked calculations for two wires a stated distance apart.Open →
• Charged particle beams and acceleratorsVelocity selector, how a linear accelerator accelerates a charged particle and structure and action of a cyclotron.Open →

What you need to know

Answer each one before you reveal it.

Take Magnetic Fields further

The same content, four other ways.

Questions from this topic

Each one with the model answer underneath.

1. 1

   What is the motor effect?

   Model answer

   The motor effect is the force felt by a current-carrying conductor placed in a magnetic field. The force acts at right angles to both the current and the field.

2. 2

   State Fleming's left-hand rule.

   Model answer

   Hold the thumb and first two fingers of the left hand mutually at right angles. The First finger points along the magnetic Field, the seCond finger along the conventional Current, and the thuMb then gives the direction of the force or Motion.

3. 3

   Why must conventional current, and not electron flow, be used with Fleming's left-hand rule?

   Model answer

   The rule is defined for conventional current, taken to run from positive to negative. Electrons drift the opposite way, so using their direction would give the force reversed.

4. 4

   A wire carries current from left to right and the magnetic field points into the page. In which direction does the force on the wire act?

   Model answer

   The force acts vertically up the page. Pointing the first finger into the page and the second finger to the right puts the thumb of the left hand upwards.

5. 5

   A wire carries current vertically downwards in a horizontal magnetic field pointing north. In which direction does the force on it act?

   Model answer

   The force acts horizontally towards the east. With the first finger pointing north and the second finger pointing downwards, the thumb of the left hand points east.

6. 6

   What happens to the direction of the force on a current-carrying wire if the current is reversed while the field stays the same?

   Model answer

   The force reverses direction. Reversing either the current alone or the field alone flips the force.

What is inside Levo

Six ways to work the same material.

Magnetic Fields revision questions

What does Magnetic Fields cover in Eduqas A-Level Physics?

7 subtopics: the motor effect and fleming's left-hand rule, f = bil sinθ and measuring magnetic flux density, the force on a moving charge, f = bqv sinθ, the hall effect and the hall probe, magnetic fields due to a straight wire and a solenoid, forces between current-carrying conductors and charged particle beams and accelerators. Each one has its own page with questions and model answers.

How is Magnetic Fields organised?

By the Eduqas A420QS specification, subtopic by subtopic, so it matches the order you are taught it in.