levo

Magnetic Fields

Magnetic fields around currents

  • 3 things to know
  • Unit A2 2

Overview

Magnetic field inside a long solenoid, field outside a long solenoid and three ways of increasing the field strength inside a solenoid.

What you need to know

Answer each one before you reveal it.

Your recallNot started
Key term

Describe the shape of the magnetic field around a long straight current-carrying wire.

Key term

How does the field around a straight wire change if the current is increased?

Key term

Describe the shape of the magnetic field produced by a current in a flat circular coil.

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    Describe the shape of the magnetic field around a long straight current-carrying wire.

    Model answer

    The field lines are concentric circles centred on the wire and lying in planes at right angles to it.

  2. 2

    How is the direction of that field found?

    Model answer

    By the right-hand grip rule: with the right thumb pointing along the conventional current, the curled fingers give the direction of the field lines.

  3. 3

    How does the strength of the field around a straight wire change with distance from it?

    Model answer

    It weakens as the distance increases, which is shown by the circles being drawn further apart further from the wire.

  4. 4

    How does the field around a straight wire change if the current is increased?

    Model answer

    The field becomes stronger at every point, in direct proportion to the current.

  5. 5

    Describe the shape of the magnetic field produced by a current in a flat circular coil.

    Model answer

    The lines pass through the centre of the coil at right angles to its plane and loop round outside it, so the coil behaves like a short bar magnet.

  6. 6

    Describe the magnetic field inside a long solenoid.

    Model answer

    It is uniform, strong and parallel to the axis of the solenoid, with the field lines evenly spaced along the inside.

Other ways to work this

The same content, four other ways.

What is inside Levo

Six ways to work the same material.

1Closed book
2Open book
3Closed book

The 3-step method, run for you

Answer cold, learn it, then prove it stuck. Levo tracks the jump between your first attempt and your last.

Physical Quantities, Scalars and Vectors
Moments and Equilibrium
Linear Motion and Dynamics
Newton's Laws of Motion

Cram a whole paper in one sitting

Sort every topic into what you know and what you do not, then drill only the weak ones.

The quarks and the .
leptonshadronsmesons

Blank Blitz makes facts automatic

Rapid timed gap-fills on the terms and numbers you need to recall without thinking.

AA current I is a charge q passing in time t.
BThe length l is vt.
CBIl becomes B × (q/t) × vt, which is Bqv.

Build It gets the exam shape right

Assemble a full-mark answer from its marking points, in the order an examiner wants them.

Coulomb is a quantity of charge.
TrueFalse

Test It catches misconceptions

Spot the fault in a statement. The traps are the mistakes students actually make.

721941163128510

Brain Breaks between sessions

Short focus games to reset attention, so the next set lands better than the last.

Every question in Magnetic Fields, on a schedule.

Attempt a question from memory, write the correct version, then attempt it again. Levo records the jump between your first attempt and your last, and brings each question back on the day you are due to forget it.

Or £46 a year, about £3.83 a month. Cancel anytime.