Solenoid Working Model

Quick Answer: The Solenoid Working Model is a coil of insulated copper wire wound along a tube and mounted on a base with two terminals. Connected to a low-voltage DC supply, it produces a magnetic field like a bar magnet’s, which students explore with compasses, iron filings and an iron core.

The Field Inside and Around a Coil

In the listing image the solenoid working model is a long coil of copper wire wound on a tube, held between end caps above a yellow base fitted with red and black terminals. When current flows, each turn of wire produces a small magnetic field, and because the turns lie side by side their fields add together. Inside the coil the field is strong and nearly uniform, running along the axis; outside it loops round from one end to the other, just as it does around a bar magnet.

Which end becomes the north pole depends on the direction of the current. The right-hand grip rule gives it: curl the fingers of the right hand round the coil in the direction of the conventional current and the thumb points to the north pole. Swap the leads at the terminals and the poles change places, as a plotting compass held at each end will show.

The strength of the field increases with the current and with the number of turns per unit length, and it rises sharply when an iron core is placed inside because the iron becomes magnetised. That is the basis of electromagnets, relays, door locks and the plunger solenoids used in valves. The recommended supply voltage and any core supplied should be checked at enquiry.

Experiments with the Solenoid

• Mapping the field pattern with plotting compasses or iron filings on a card
• Identifying the poles and reversing them by reversing the current
• Comparing field strength with and without an iron core
• Showing a soft-iron rod being pulled into the coil when the current is switched on

Care & Handling

• Use only short periods of current, since the solenoid working model warms up if left connected.
• Tighten the terminals by hand only; overtightening strips the threads.
• Keep iron filings in a sealed tray or under card so they do not collect on the coil.
• Store the model dry to protect the enamel insulation and terminals.

Specifications

Why Choose LabEquip

Physics teachers buy a demonstration solenoid for the electromagnetism topic because it makes the link between a coil and a bar magnet visible. LabEquip lists this model in the STEM kits range with the Magnetic Effect of Current apparatus, which starts the same topic with the field produced by a current. Use the contact page for your enquiry.

Frequently Asked Questions

How do I find the north pole of the solenoid?

Use the right-hand grip rule: wrap your right-hand fingers around the coil in the direction of the conventional current, and your thumb points to the north pole. Check it with a plotting compass, whose north-seeking end points away from the north pole outside the coil.

Why does an iron core make the solenoid stronger?

Iron is ferromagnetic. The coil’s field lines up the magnetic domains in the iron, and the magnetised iron adds its own field to the coil’s. Soft iron is used because it loses its magnetism quickly when the current stops.

What is the difference between a solenoid and an electromagnet?

A solenoid is the coil itself. When a soft-iron core is placed inside to strengthen and concentrate the field, the combination is usually called an electromagnet. The word solenoid is also used for coil-and-plunger actuators in locks and valves.

Which power source suits the solenoid?

Use a low-voltage DC bench supply or a pack of cells, together with a switch and, ideally, a rheostat for setting the current. Keep the current modest and disconnect it once each reading is taken, so the winding stays cool.

How can students show the field pattern?

Place a card over or through the coil, sprinkle iron filings thinly and tap the card gently while the current flows. The filings line up along the field. Plotting compasses placed around the coil show the direction as well as the shape.

Does the number of turns matter?

Yes. For the same current, more turns per unit length give a stronger field inside the coil. Comparing coils with different numbers of turns is a classic fair-test investigation on electromagnet strength.

Last Updated: September 2026