Electromagnets - What are they?
An electromagnet is a type of magnet that uses an electric current to generate a magnetic field. Unlike permanent magnets, these only exhibit magnetic properties when an electric current is flowing through them.
The construction typically involves a coil of wire, often wound around a ferromagnetic core. When an electric current passes through the coil, a magnetic field is produced. The strength of the magnetic field can be controlled by adjusting the current flow through the coil.
The key characteristics include:
1. On/Off Capability: The magnetic field of an electromagnet can be easily turned on or off by controlling the flow of electric current.
2. Adjustable Strength: The strength of the magnetic field generated by an electromagnet can be adjusted by varying the current passing through the coil. Increasing the current increases the magnetic field strength, while decreasing the current weakens it.
3. Temporary Magnetism: Electromagnets lose their magnetic properties once the electric current is switched off or interrupted.
Electromagnets have numerous practical applications across various industries. Some common examples include:
– Electric Motors and Generators: Electromagnets are used in electric motors and generators to convert electrical energy into mechanical energy or vice versa.
– Magnetic Separators: Electromagnets are employed in magnetic separators to attract and separate magnetic materials from non-magnetic ones.
– Magnetic Resonance Imaging (MRI): The powerful magnetic fields required for MRI machines are generated using superconducting electromagnets.
– Loudspeakers and Microphones: Electromagnets are used in speakers and microphones to convert electrical signals into sound waves or vice versa.
– Magnetic Lifters and Magnetic Chucks: Electromagnets are utilized in lifting and holding applications where temporary magnetic strength is required.
Overall, the ability to control and adjust the magnetic field makes electromagnets highly versatile and widely used in various technological applications.
A practical visiual
When an uninterrupted electrical current is applied to a steel conductor, a magnetic field is generated:
The polarity of the coil can be reversed to alter the magnetic field:
The activated coil produces the magnetic field, enveloping the inductor (the coiled part) as continuous current flows through it.
In the absence of current through the coil,
there is no magnetic field, allowing the part to remain free:
By supplying a continuous current to the coil,
a magnetic field is established, resulting in the secure holding of the part: