✓ Revise Right course
A solenoid is a coil of wire that produces a magnetic field when current flows through it. Free GCSE AQA Physics notes with key definitions and 15 FAQs.
Solenoids and Electromagnets is part of The motor effect in GCSE AQA Higher Physics.
5 min
Reading time
19
Lessons in this topic
GCSE AQA Higher
Pathway
Reviewed by Revise Right
Content review
A solenoid is a coil of wire that produces a magnetic field when current flows through it. Free GCSE AQA Physics notes with key definitions and 15 FAQs.
AQA GCSE Physics mock draft, 26–31 Oct. Draft coverage: Physics Paper 1 (Higher tier). Reviewed for an original-practice sitting; check student availability before registering. Marking and results will follow later, after separate approval. Eligible new accounts receive a five-day Pro trial when signup email verification completes. Previous trials keep their original expiry. After expiry, new papers need Pro unless you have an explicitly confirmed free sitting offer for this event. That offer adds no Pro time or AI learning. Saved attempts and released results remain readable. No card or automatic charge.
Use this lesson to stay inside The motor effect while connecting the detail back to the wider Magnetism and electromagnetism topic.
Read the core explanations from Solenoids and Electromagnets before testing yourself from memory.
You've seen how a single wire carrying current creates a weak magnetic field around it. But what if we could amplify that effect dramatically? That's exactly what happens when we coil the wire into a specific shape.
Picture wrapping a wire around a pencil in tight, even loops. When current flows through this coiled wire, something remarkable happens. Instead of weak, scattered magnetic field lines, we get a concentrated, powerful magnetic field that behaves just like a bar magnet.
This coiled arrangement is called a solenoid, and it's the foundation of countless devices you use every day. From the starter motor in cars to the speakers in your headphones, solenoids convert electrical energy into magnetic force.
When you coil a wire, you're not just changing its shape - you're fundamentally changing how the magnetic fields interact. Each loop of wire creates its own circular magnetic field. But here's the clever part: when these loops are close together, their individual fields combine and reinforce each other.
Think of it like voices in a choir. One person singing alone is barely audible from the back row. But when dozens of voices sing the same note together, the sound becomes powerful and clear. Similarly, each loop of wire adds its magnetic field to the total effect.
Inside the solenoid, all these individual circular fields point in the same direction and add up. This creates a strong, uniform magnetic field - meaning the field lines are parallel and evenly spaced, just like inside a bar magnet.
The magnetic field pattern around a solenoid is distinctive and predictable. Outside the coil, the field lines curve from one end to the other, forming the classic bar magnet pattern. One end becomes a north pole, the other becomes a south pole.
You can predict which end is which using the right-hand rule. Point your right thumb in the direction of conventional current flow around the coil. Your fingers curl in the direction the current flows, and your thumb points toward the north pole of the solenoid.
Inside the solenoid, the field is remarkably uniform - the field lines run straight and parallel from south to north. This uniform field is incredibly useful in applications where you need consistent magnetic strength across a region, like in MRI machines or particle accelerators.
Complete the sentence: A solenoid is a coil of wire that produces a magnetic field when current flows through it.
A solenoid on its own is powerful, but we can make it even stronger. When you slide an iron core into the centre of the solenoid, the magnetic field strength increases dramatically - often by factors of hundreds or thousands.
Iron is a ferromagnetic material, which means it becomes strongly magnetised when placed in a magnetic field. The iron core doesn't create its own magnetic field, but it amplifies the field created by the current in the coil. Think of it as a magnetic amplifier.
This combination - a solenoid with an iron core - is called an electromagnet. Unlike permanent magnets, electromagnets can be switched on and off by controlling the current. They can also be made much stronger than permanent magnets of the same size.
Electromagnets are everywhere in modern technology because they offer precise control over magnetic forces. In a car's starter motor, electromagnets create the rotating magnetic field that turns the engine over. In speakers, an electromagnet attached to a cone vibrates to create sound waves.
Scrapyard cranes use massive electromagnets to lift and move steel. The operator can pick up a car by switching on the electromagnet, move it to a new location, then drop it by switching off the current. Try doing that with a permanent magnet!
Electric bells work by using an electromagnet to pull a striker against a bell. When you press the button, current flows through the electromagnet, which attracts an iron armature. This breaks the circuit, switching off the electromagnet, so the armature springs back and the cycle repeats rapidly.
Worked example: How an Electric Bell Works
Trace the sequence of events when someone presses an electric doorbell button.
Answer: The electromagnet repeatedly switches on and off, creating a vibrating motion that rings the bell continuously.
Exam questions often test your ability to interpret electromagnetic device diagrams. The key is to identify the solenoid, trace the current path, and predict the magnetic poles using the right-hand rule. Remember that reversing the current direction reverses the poles.
When explaining how electromagnets work, examiners want to see three key points: current creates a magnetic field, the solenoid shape concentrates this field, and the iron core amplifies it. Don't just say 'it becomes magnetic' - explain that the iron becomes magnetised by the field from the current.
For device explanations, work systematically through the sequence of events. Start with the input (usually pressing a switch), follow the current path, identify what the electromagnet does, and explain the final output or movement.
This interactive activity has been removed due to technical issues.
Published by Revise Right. Use the official specification reference to check the requirements for your course. Content updated: 2026-03-20.
Move to the related lessons or back to the topic page when you need the wider sequence before exam-style practice.
A solenoid is a coil of wire that produces a magnetic field when current flows through it. The fields from each loop combine and reinforce each other, so the magnetic field inside is strong and uniform.
An electromagnet is a solenoid with an iron core that can be switched on and off by controlling the electric current. The iron becomes magnetised by the field from the current and increases the field strength dramatically.
Outside a solenoid, the field lines curve from one end to the other like those of a bar magnet, so one end is a north pole and the other a south pole. Inside, the field is uniform: the lines run straight and parallel. Reversing the current reverses the poles.
An electromagnet can be made stronger by adding an iron core, which can increase the field strength by factors of hundreds or thousands. More turns of wire and a bigger current also increase the strength of the magnetic field.
Pressing the button lets current flow through an electromagnet, which attracts an iron armature so the striker hits the bell. This breaks the contact and switches off the electromagnet, so a spring pulls the armature back, the contact remakes and the cycle repeats rapidly.
A ferromagnetic material, such as iron, becomes strongly magnetised when placed in a magnetic field. An iron core does not create its own field but amplifies the field from the current in the coil.
Electromagnets can be switched on and off by controlling the current, and they can be made much stronger than permanent magnets of the same size. This gives precise control over magnetic forces.
Solenoids are used in car starter motors, speakers in headphones, electric bells and scrapyard cranes, converting electrical energy into magnetic force. Their uniform field is also useful in MRI machines.
Coiling a wire makes the magnetic field stronger because each loop creates its own circular field, and when the loops are close together their fields combine and reinforce each other. Inside the solenoid they all point the same way and add up.
The magnetic field inside a solenoid is strong and uniform: the field lines are parallel and evenly spaced and go from south to north, just like inside a bar magnet. This is useful in MRI machines and particle accelerators.
A solenoid behaves just like a bar magnet: outside the coil the field lines curve from one end to the other, with one end a north pole and the other a south pole. Inside, the field is uniform.
Reversing the current direction in a solenoid reverses its magnetic poles, so the north and south ends swap. The poles are predicted with the right-hand rule.
Electromagnets can be switched on and off by controlling the electric current, unlike permanent magnets. A scrapyard crane picks up a car by switching the electromagnet on, then drops it by switching the current off.
Sliding an iron core into a solenoid increases the magnetic field strength dramatically, often by factors of hundreds or thousands. The iron becomes magnetised by the field from the current, acting as a magnetic amplifier.
An electromagnet is explained with three key points: the current creates a magnetic field, the solenoid shape concentrates this field, and the iron core amplifies it because the iron becomes magnetised by the field from the current.