HomePhysicsP6: Magnetism and ElectromagnetismP6.2 Electromagnets – Coils and Current

P6: Magnetism and Electromagnetism

P6.1 Magnetism – Magnets and Magnetic FieldsP6.2 Electromagnets – Coils and CurrentP6.3 The Motor Effect and Electric MotorsP6.4 Generators and Transformers
P6: Magnetism and Electromagnetism

Electromagnets – Coils and Current

Learn how electric current creates magnetic fields and build powerful electromagnets

Electromagnet coil

Electromagnets

Magnetism from electricity

How Electromagnets Work
Creating magnetism from electric current

An electromagnet is a coil of wire (called a solenoid) that produces a magnetic field when electric current flows through it. The field inside the coil is strong and uniform, similar to a bar magnet with a North and South pole.

A current-carrying wire creates circular magnetic field lines around it. When the wire is coiled, these fields combine to create a stronger field along the axis of the coil.

Increasing Electromagnet Strength
Three key factors

The magnetic field strength of an electromagnet can be increased by:

⚡

More Current

Higher current = more field

🔄

More Turns

More coil loops = stronger field

🔩

Iron Core

Amplifies field ~10×

The Right-Hand Rule
Determining pole direction

To find the direction of the magnetic field:

For a solenoid: Curl your right hand fingers in the direction of current flow around the coil. Your thumb points toward the North pole.

For a straight wire: Point your thumb in the direction of current. Your fingers curl in the direction of the magnetic field (concentric circles).

Electromagnet Builder
Adjust current, turns, and core material to see how field strength changes

Higher current = stronger magnetic field

More turns = stronger magnetic field

Amplifies field strength by ~10×

ONNS
Field Strength250 units

Right-Hand Rule

Curl your fingers in the direction of current flow around the coil. Your thumb points toward the North pole of the electromagnet.

Applications of Electromagnets
Where electromagnets are used
  • Scrapyard cranes: Pick up and release metal using switchable magnetism
  • Relays: Electromagnetic switches that control larger currents
  • Electric bells: Electromagnet attracts striker, breaks circuit, repeats
  • MRI machines: Powerful superconducting electromagnets for medical imaging
  • Maglev trains: Electromagnetic levitation for frictionless travel
Key Terms Flashcards
Click the card to reveal the definition

Electromagnet

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Worked Example
Increasing electromagnet strength

Question:

An electromagnet with 50 turns carrying 2A current needs to be made stronger. Suggest three ways to increase its strength.

Answer:

  1. Increase the current – e.g., from 2A to 4A (doubles the field)
  2. Add more turns – e.g., from 50 to 100 turns (doubles the field)
  3. Add an iron core inside the coil (amplifies field by ~10×)

The most effective single change is adding an iron core, as it provides the greatest increase in field strength.

Test Your Knowledge
Question 1 of 6

What three things increase the strength of an electromagnet?