Consider a coil of insulated copper wire, wound on a soft iron core, we will put some iron nails on the table and get the coil near the nails notice what happens, now connect a 9V battery across the terminals of the coil and now notice how the coil behaves magically like a magnet and attracts the iron nails, repeat this experiment with more number of turns and a stronger battery. Notice how the strength varies.
A current carrying conductor in the shape of a coil behaves like a magnet and this property of a conductor is called as electromagnetism, an electromagnet is different from a regular permanent magnet is that the electromagnet can be turned on and turned off as we want.
The strength of an electromagnet depends on the number of turns of the coil, a single wire does not create enough magnetic field around the conductor to attract the iron nail on the table, therefore, the conductor is coiled many times and hence, the magnetic field induced is multiplied by the number of turns, the strength of magnetic field induced also depends on the amount of current flowing through the conductor.
Let us look at some of the applications of this effect in our day to day life.
Can crusher: the field generated by an electromagnet is powerful it can easily crush a can without even touching, the can look at how the can has deformed, the can is placed inside a
coil and when the coil is energized the can tries to bend in the shape of the magnetic lines of force, deforming the can further by applying more force can compress the can into a flat disc.
Magnetic cranes: the garbage we throw sometimes contains metals which can be recycled, and some metals that might take many years to biodegrade hence we use a huge electromagnet connected to the end of a crane and swing it across the garbage, all metal object get attracted and stick to the electromagnet and can easily be separated within seconds, when all the metals are lifted up the crane will then de-energize and the metals are collected at a separate place. Before the invention of electromagnets, permanent magnets were used to do the same job, where the metal objects were removed manually.
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