We know that a magnetic compass responds to a magnet placed near it. In this section, we investigate whether an electric current can also influence a magnetic compass, indicating a magnetic effect.
A magnetic compass contains a tiny magnet that responds to magnetic fields. When electric current flows through a wire, it creates a magnetic field around it. This magnetic field acts on the compass needle and causes it to deflect. When the current stops flowing, the magnetic field vanishes and the compass needle aligns itself with Earth’s magnetic field again.
Magnetic effect of electric current:
The phenomenon in which a current flowing through a conductor produces a magnetic field around it is called the magnetic effect of electric current.
Magnetic field:
The region around a magnet or a current-carrying conductor where its magnetic influence can be detected, such as by the deflection of a compass needle, is called a magnetic field.
Magnetic field around a current-carrying conductor
Scientist behind the discovery:
In 1820, the Danish scientist Hans Christian Oersted discovered that an electric current can produce a magnetic field. While demonstrating an electric circuit, he noticed that a nearby compass needle deflected whenever the circuit was switched on or off. This experiment proved the link between electricity and magnetism, leading to further scientific developments.
Applications of magnetic effect of electric current:
- Electromagnets
- Electric bells
- Transformers
- Induction cookers and stoves
- Junkyard cranes
- MRI (Magnetic Resonance Imaging)
- Electric motors
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Fans
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Loudspeakers
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Relays
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Generators
Electromagnet:
An electromagnet is a temporary magnet produced when electric current flows through a coil of wire, generally wound around a soft iron core. The magnetic field exists only as long as the current flows and disappears when the current is switched off. The strength of an electromagnet can be increased or decreased by changing the current or the number of turns of the coil, and its magnetic poles can be reversed by reversing the direction of current.
Electromagnet:
An electromagnet is a temporary magnet formed when electric current flows through a coil of wire wound around a soft iron core, which becomes magnetic only while the current is flowing.
Strength of an electromagnet:
The strength of an electromagnet is the intensity of its magnetic field produced by a current-carrying coil, which increases when a soft iron core is inserted and exists only as long as electric current flows.
Poles of an electromagnet:
The poles of an electromagnet are the two opposite magnetic ends produced at a current-carrying coil, whose polarity depends on the direction of electric current and disappears when the current is switched off.
Factors affecting the strength of an electromagnet:
- Increasing the number of cells increases the current and strengthens the electromagnet.
- Increasing the number of turns of the coil increases the magnetic field.
- Changing the direction of current reverses the poles of the electromagnet.
Lifting electromagnets:
Lifting electromagnets are powerful electromagnets attached to cranes. When electric current is switched ON, the electromagnet becomes strong and can lift heavy iron or steel objects. When the current is switched OFF, the magnetic field disappears and the objects are released. These electromagnets are commonly used in factories and scrap yards to lift, move, and sort heavy metal items efficiently.
Lifting electro magnets
Earth as a magnet:
The Earth itself behaves like a giant magnet. Deep inside the Earth, the movement of molten iron in the core produces electric currents, which create Earth’s magnetic field. Many birds and animals use this magnetic field for navigation. This field also protects the Earth by deflecting harmful charged particles coming from space.