Download Electromagnet Notes

Electromagnet Notes
1. What is an electromagnet?
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A temporary magnet made of a wire coil through which an electric current passes
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How does it work?
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History:

In 1820, Hans Christian Oersted, a Danish Physics Teacher observed that
the electrical current moving through a circuit moved the needle of a
compass. When he reversed the current the needle was deflected in the
opposite direction. When the current was cut off, the compass worked
normally. Oersted hypothesized that the electrical current produced a
magnetic field around the wire.
Arrows show the
direction of the
magnetic field
around the circuit
Electric Current

Design – By wrapping a wire around an iron core and attach the wires to
an electrical source will produce a temporary magnetic field around the
iron.

To improve on this design one would need to either add more
current to the wire and/or add more coils around the iron
2. Magnetism can be used to measure voltage and current:
- Galvanometers use electromagnets to detect electrical currents
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When current flows through the coil, the magnetic force causes the coil to rotate.
The greater the current the greater the rotation. Attached to the coil is a needle
and the movement is measured on a scale.
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2 Types of galvanometers:
1. Ammeters – measure the electrical current passing through a circuit
- Generally connected in series
2. Voltmeters – measure the potential difference of a circuit
- Generally connected in parallel
3. In 1831 a British scientist, Michael Farraday and an American Scientist Joseph Henry found that by
moving a wire through a magnetic field induced an electric current in that wire
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This is known as Electromagnetic Induction
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The process by which moving a wire through a magnetic field produces a current
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Not only can magnetism be derived from electricity, electricity can be derived
from magnetism.
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What does this technology offer
 By using magnetic forces we can now utilize magnetism to power many
household items
How can we utilize electromagnetic induction in our homes
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Electromagnetic induction is how a generator works!!!!
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What is a generator?

A device that produces an electric current by rotating a loop of wire in a
magnetic field

Or a device that uses electromagnetic induction to produce an electric
current
How is a generator different from an electric motor?
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Generators use electromagnetic induction to produce electricity, while motors use
electromagnetism to convert electricity into mechanical energy. Also the motor
needs a commutator in order to function.
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What is a commutator ?

A reversing switch that causes the poles of the rotating electromagnet to
switch
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Why would you want to switch the poles?

The electromagnets turn the coils, if the poles of the temporary
magnet do not switch when the north poles align with the south
pole the coils would no longer turn
Coil
Commutator
Brushes
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Magnet