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Magnetism(Review). Magnetic Field Lines always move out of the __________end of a magnet!. East North South West. Magnetic Field Lines always move into the __________end of a magnet!. East North South West. Where are all magnets the strongest?. At the North Pole At the South Pole
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Magnetic Field Lines always move out of the __________end of a magnet! • East • North • South • West
Magnetic Field Lines always move into the __________end of a magnet! • East • North • South • West
Where are all magnets the strongest? • At the North Pole • At the South Pole • At both Poles • Directly in the center
Magnets can be made of iron, _________, or nickel. • Copper • Carbon • Cobalt • Cadmium
Two similar poles of a bar magnet will always _____________. • attract • repel
Two opposite poles of a bar magnet will always _____________. • attract • repel
Electromagnetism --the relationship b/w electricity and magnetism
Is there a relationship between electricity and magnetism? Let’s see what I discovered!!! Hans Christian Oersted
Oersted’s Law • The flow of electricity through a wire conductor produces a magnetic field around the wire.
Right Hand Rule • The direction of the current determines the direction of the magnetic field.
2 things affect the strength of a magnetic field: • Amount of current • Increase current = increase strength • Decrease current = decrease strength • # of coils of wire • More turns of wire = more strength • Less turns of wire = less strength
I was just wondering what would happen if I slammed an iron core through a current carrying coil of wire? What did you find out?
If you take an iron core and insert it into a coil of current carrying wire, you have a temporary magnet called an electromagnet!!
Strength of an Electromagnet • 2 things affect the strength of an electromagnet(same 2 things that affect the strength of a magnetic field): • Amount of Current • # of turns of wire(# of coils)
What happens to the strength of an electromagnet if the current through the wire increases from 4 A to 9 A? • Remains the same • Increases • Decreases
Uses of Electromagnets • Electric Meters: because of their ability to detect current(only work when there is one), electromagnets are used in a variety of electric meters. • Ammeter—measures current • Wired in series • Voltmeter—measures voltage • Wired in parallel • Galvonometer—”detects” current
Uses of electromagnets(cont.) • Motors • Use electromagnets to convert electrical energy into mechanical energy • An electromagnet turns inside a permanent magnet
If current moving through a wire produces a magnetic field, I wonder…… ….What would happen if we move a wire through a magnetic field
I bet it has never been tested. Let’s try it!!! I’ll try anything once!!
Haven’t we already done that? Joseph Henry Michael Faraday
Faraday and Henry discovered that moving a wire through a magnetic field, or moving a magnetic field through a coil of wire “induced” a current on the wire!! Electromagnetic Induction—process in which moving a wire through a magnetic field produces a current on the wire.
….produces a current on a wire.“Did we just “create” electricity” • Generators—use electromagnets to convert mechanical energy into electrical energy.
Other Uses of electromagnets: Transformers Are you talking about me? Not this Kind!!!!
Alternating vs. Direct Current Alternating Current Direct Current Current only goes in one direction. • Current alternates, one direction, then the other. Plug it in, Plug it in!!
Transformers • Used to increase or decrease the voltage of alternating currents.
Transformers • Consist of 2 coils of wire. • Primary Coil • Alternating current enters • Secondary Coil • Alternating current leaves • It’s the difference in the number of turns of wire on each coil that causes the voltage the change.
2 Types of Transformers • Step-up Transformer • Increase voltage • Secondary more turns than primary • Step-down Transformer • Decrease voltage • Primary more turns than secondary
A step-up transformer has 400 turns on its primary coil and 600 turns on its secondary coil. If the primary coil is supplied with 120 V of alternating current, what will be the secondary (output) voltage? ns= 600 turns np= 400 turns Vs= ? Vp= 120
