When an electric current flows through a wire -
especially one in the form of a coil - it becomes an electromagnet. It is a
temporary magnet, as it can retain its newly-gained characteristics only as long
as the current flows through it. However, it shows all the properties of a
permanent bar magnet, including the two opposite poles - N and S - during this
This very nature of electromagnets has made
them indispensable to modern life: we can turn them on and off, as we wish
whenever we want. The simple electric bell is a case in point.
We want an electric bell to produce a ring, at
the touch of a button, only once or twice, but not for ever. So, the bell does
the job when we choose to send a current through it and afterwards the bell
When the switch 'D' is on, the circuit is complete and then 'A' becomes an electromagnet. Then
it momentarily attracts 'B' towards it and the ball at the end of it, hits the bell, producing
As 'B' was
attracted to 'A', the
current through the circuit got cut off, that in turn made it losing its magnetism.
'B' was released from
'A' to be back in
The circuit is now complete
again and the current starts flowing through it, repeating the above sequence of
events. As a result, we get a continuous ringing, as long as the switch remains
The following animation shows the
whole sequence in detail:
Please answer the following questions.
- How do you increase the strength of an electromagnet?
- Discuss the uses of electromagnets at industrial level.
- How do you destroy a magnet?
- Draw magnetic field lines around two
bar magnets, when north poles face each other. Where would you expect a neutral
- It is more appropriate to call the north pole of a magnet, a north-seeking-pole. Explain it.
- Magnetic poles are not known to have an existence in isolation. How do you explain this from molecular point of view?
- Discuss the most significant parts of an electric bell.
- How do you determine the poles of an electromagnet without a compass?
Resources at Fingertips
This is a vast collection of tutorials, covering the syllabuses of GCSE, iGCSE, A-level and even at undergraduate level.
They are organized according to these specific levels.
The most popular tutorial is the Book of Electricity, which comes at the top of Google search for electricity tutorials for GCSE / AS/ A-Level at present.
In addition, there are a few more which come at the top of Google search.They are all supported by an extensive collection of animations and interactive labs.
Stand Out - from the crowd
"There's no such thing as a free lunch."
The best things in nature are free with no strings attached - fresh air, breathtakingly warm sunshine, scene of meadow on the horizon...
Vivax Solutions, while mimicking nature, offers a huge set of tutorials along with interactive tools for free.
Please use them and excel in the sphere of science education.
Everything is free; not even registration is required.