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Electromagnetism Review
1. What is magnetic force? The force where objects are attracted or repelled to one another
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What is a magnetic field? The area around a magnet that behaves like a magnet
What are magnetic poles? The ends of the magnet, there are always two poles a north pole and a south pole
What happens when like poles are placed next to each other? They repel each other.
What happens when opposite poles are placed next to each other? They are attracted to each other.
What is the direction of a magnetic field? North to South
Where is the magnetic field around a magnet the strongest? Strongest at the poles
Where is it the magnet field around a magnet the weakest? weakest around the middle
How are magnetic field lines an indication of the strength of a magnet? The farther apart the lines, the weaker
the field strength. The magnet gets weaker the farther away it is.
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What are three similarities between electrical charges and magnetic poles?
Likes repel and opposites attract
They are both non-contact forces
They both have field lines which show direction
What are the differences between electrical charges and magnetic poles? Charges can stand alone and magnetic
poles can not (you must have both a north and a south)
12. How can you strengthen a magnet? By aligning the domains in the same direction with another magnet or by
using electricity
13. How can you weaken or demagnetize a magnet? Make the domains come unaligned by dropping it or heating it.
14. What are magnetic domains? Groups of atoms that act like tiny magnets and when they align the object
becomes magnetized.
15. What happens to the domains in a permanent magnet? The domains remain aligned in the same direction and
the magnet stays magnetized.
16. What do the domains look like in a non-magnetized material? The domains are not lined up they are all going in
random directions.
17. What instrument is used to detect a magnetic field? Compass
18. Describe what happens to a magnet if it is broken or cut into parts. Each half or part becomes a magnet each
with two poles.
19. Why is the Earth magnetic? The outer core is made of molten iron and nickel which flows in convection currents.
This causes the magnetic field of the earth.
20. What is meant when someone says a compass is North seeking? Explain in terms of both magnetic and
geographic poles. The north pole of a compass is attracted to its opposite, Magnetic South which is also
geographic north.
21. What factors affect the magnetic strength of an electromagnet?
a. The number of coils
b. The strength of the current
c. The material that makes up the core.
22. A proton with a charge of 1.6x10-19C is sailing along inside a cyclotron at 2.99 x 107m/s experiences a
perpendicular magnetic field of 3.8T. What is the magnitude of the force it will experience?
F=qvB
F = 3.8 x (1.6x10-19 ) X (2.99 x 107)
F = 1.82 x 10-11N
23. A proton moves in a uniform magnetic field with a speed of 10 7 m/s and experiences a magnetic force
of 32N. The charge of a proton is 1.6x10-19C. Determine the magnitude of the magnetic field.
B = 32/(1.6x10-19 X 107)
B = 2 x 1013T
24. An electron moves with a force of 2.56x10-13 N through a magnetic field of 0.080T. What is the velocity
of the electron? Its charge = 1.6 x 10-19 C.
0.08 = 2.56x10-13 /(1.6x10-19 * v)
v = 2 x 107m/s
25. Label the diagram of the Earth below and draw the direction of the field lines for the magnetic south and north
poles.
A = Magnetic South Pole
B = Geographic North Pole
C = Geographic South Pole
D = Magnetic North Pole
26. Draw the magnetic field lines with arrows around the magnet diagrams below: Draw the North needle for the
compass direction in the four circles.
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27. How do you induce a current in a wire?
Moving a magnet in and out of coil of wire- a moving magnetic field induces a charge
28. What produces a magnetic field?
Bar magnet- a moving charge
Electromagnet- a current
29. Explain the right hand rule. What does the thumb point to? What do your fingers represent and point to?
The thumb points to current. The fingers wrap around and point in the direction of the magnetic field.
30. What was Oersted known for discovering?
He connected electricity with magnetism. He discovered that adding a current through a wire produced a
magnetic field and is proved by using a compass around the wire. The compass points in a circle around the wire,
indicating the presence of a magnetic field.