Unit 4 Review for Electromagnets

Unit 4 Review for Electromagnets

By Rochelle Hogan

​Unit 4 Assessment for Turner MS (2nd Period)

By Rochelle Hogan

How did the moving parts of a speaker help us understand how electromagnetism works?

​Let's discuss....

By Rochelle Hogan

Parts of a speaker

Summary: ​The moving parts have been circled: The permanent magnet has a magnetic field that reacts to the force from the magnetic field of the coil (voice coil) as the current flows through it, and the cone is moved in a back and forth (vibration like pattern) by the magnet and coil to help create sound.

By Rochelle Hogan

Parts of a speaker

When the coil is connected to a sound source, like a computer or phone (electrical signal), the cone begins to move backwards and forwards creating air pressure to move (sound waves). That movement is seen as a vibration. That vibration is what causes the sound that we hear.

By Rochelle Hogan

Parts of a speaker

The coil has to be connected to a battery or some type of sound source in order to create a force.

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​Hint! An electromagnet is a type of magnet in which the magnetic field is produced by an electric current expressed in volts (voltage) that is a measurable force.

By Rochelle Hogan

​Force Between Magnets

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A push between two magnets is called repulsion (repel)

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A pull between two magnets is called attraction (attract)

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By Rochelle Hogan

​Force Between Magnets

​The north and south poles are attracting to each other (pulling towards).

The south and south poles and north and north poles are repelling each other (pushing away from)​.

By Rochelle Hogan

​Energy Magnets Produce

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Kinetic energy is the movement energy of an object. Kinetic energy can be transferred between objects and transformed into other kinds of energy. Can you explain how the speaker parts relate to kinetic energy? (Kinetic energy is present when the magnet and coil's magnetic field produce a force and causes air pressure to move back and forth which is the vibration of sound waves)

​Hint: Magnetic fields transfer energy. The presence of a magnetic field indicates magnetic energy. This energy is observed by the speed of mass. This speed is a movement of energy. For an observer, kinetic energy exists only if there is movement.

By Rochelle Hogan

​Magnetic Fields

​Magnetic fields have a 3D shape. Notice the iron filings before the bar magnet is added. Then notice the filings after the bar magnet is added. The filings appear to gather AROUND the magnet in a 3D shape.

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​Before the Bar Magnet is Inserted

​After the Bar Magnet is Inserted

By Rochelle Hogan

​Magnetic Fields

​Since magnetic field lines are the path taken by a North Pole when it is in range of a magnetic field of another magnet, it is clear that the direction of the North Pole would be from North Pole to South Pole of a magnet. The North Pole of a magnet will repel the North Pole inside and would be attracted by the South Pole of the magnet. Thus creating a dimensional shape.

By Rochelle Hogan

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The closer you stand to a magnet, the stronger the magnetic field will be. The farther away you are from a magnet, the weaker the magnetic field becomes. (A magnetic field never ends – it simply gets weaker and weaker the farther away you go, even to infinity!)

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​The Strength of Magnets

By Rochelle Hogan

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In Summary: ​When we change the distance we change the energy between magnets in the magnetic field.

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~​The bigger the magnet, the stronger the magnetic field around it.

~The shorter the distance between the magnets, the stronger the magnetic field around it.

~The more coils in an electromagnet, the stronger the magnetic field.

~The thicker the coils, the stronger the magnetic field around it. ​

By Rochelle Hogan

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An electromagnet is a type of magnet in which the magnetic field is produced by an electric current. Electromagnets usually consist of wire wound into a coil. The current comes from a battery. The magnetic field disappears when the current is turned off. The strength of an electromagnet changes depending on the size and amount of the attached battery/batteries.  A higher voltage battery/batteries will produce a larger current through the same wire. Also, the more batteries, the more power.

​The Strength of ElectroMagnets

By Rochelle Hogan

​The Strength of ElectroMagnets

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More current = more energy = more force ​

When you change the current you change the shape in an electromagnet. ​

By Rochelle Hogan

Summary

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Can you summarize everything we have learned about magnets and electromagnets? How does all this information relate to the speaker we started with? What are the moving parts and how do they relate to magnets and electromagnetism we have investigated? Make a connection using all of the vocabulary terms we have gone over so far: force, kinetic energy, magnetic field, electromagnets, attract (attraction), repel (repulsion), distance, coil, battery, iron core, vibration, magnetism... ​

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