Download Unit #8: Magnetism Review Sheet

Name:
Date:
Mr. Rodriguez
Physics is Life
Chapter 25/26: Problem Set #1
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Magnetic poles are similar to a coupling of a positive and negative charge. Magnetic field lines (going from the north
to the south pole) represent the direction a single north pole would move if placed within the magnetic field. However,
unlike charges, magnetic monopoles (a single north or south pole) has never been observed.
Moving charge generates a magnetic field. If there is a magnetic field, moving charge is involved.
A charge moving within a magnetic field will experience a magnetic force.
 FM = qvB (here q is the charge, v is the velocity of the charge in m/sec, and B is the magnitude of the magnetic
field measured in Teslas = T = N/(A-m)
 In this equation, v is the component of the velocity that is perpendicular to the magnetic field. If the velocity is
parallel to the magnetic field, it will experience no force.
 Use the right hand rule to determine the direction of this force: your fingers point in the direction of the magnetic
field, your thumb points in the direction of the velocity of the charge, your palm will then be in the direction of the
force applied TO A POSITIVE CHARGE. This force is reversed if the charge is negative.
A wire carrying current within a magnetic field will experience a force on it.
 FM = iLB (i is the current in the wire in Amps, L is the length of the wire in meters, and B is the magnetic field).
 For this relationship, current (or L) must be perpendicular to the magnetic field.
 The more general relationship: FM = iLB(sin) where  is the angle between the wire and the magnetic field.
A current within a wire produces a magnetic field around the wire.
 Bwire = (o/2)(i/r) where i is the current in the wire, r is the distance from the wire, and o is a constant = 4 x 10-7
T-m/A.
 The orientation of the magnetic field produced by a wire is determined by the right-hand rule: grab the wire so
that your thumb is pointing in the direction of conventional positive current. Your fingers, as they curl around the
wire, will then become the orientation of the magnetic field.
A magnetized bar has its power concentrated at two ends, its poles; they are known as its north (N) and south (S)
poles, because if the bar is hung by its middle from a string, its N end tends to point northwards and its S end
southwards. The N end will repel the N end of another magnet, S will repel S, but N and S attract each other. The
region where this is observed is loosely called a magnetic field
Either pole can also attract iron objects such as pins and paper clips. That is because under the influence of a nearby
magnet, each pin or paper clip becomes itself a temporary magnet, with its poles arranged in a way appropriate to
magnetic attraction.
1. Magnetism is always present when electrical charges ______________
2. The _____________ pole of a compass is used to determine the direction of a magnetic field.
3. Label the left side of this bar magnet north and the right side south. Draw the magnetic field around
the bar magnet. Be sure to show the direction of the flux lines.
4. Where is the magnetic field strongest? __________What do the flux lines look like there?
Unit #8 Magnetism Review Sheet
5. Draw the flux line pattern between opposite (N and S) and like poles (N and N, S and S).
6. Draw the flux lines around this conductor with current moving to the right.
7. Where is the north pole of this solenoid?
8. A wire with current is placed within a magnetic field. The current in the wire is directed towards the top
of this page. What is the direction of the magnetic force on the wire?
9.Explain how to use a battery, a switch, and a coil of wire to magnetize a piece of steel?
10. State the right hand rule for determining the direction of the magnetic field lines of force around a current-bearing
wire? (b) What effect does reversing the current in the wire have on the magnetic field around it?
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Unit #8 Magnetism Review Sheet
11. What is the magnetic induction (B) at a point 0.8m from a straight wire carrying a current of 2A?
12. Sketch the appearance of a compass (north end) between two like poles and unlike poles of a magnet.
13. (a) Describe how the picture below helps one to find the force of a positive charge moving in a magnetic field.
14. Describe how you would use a wire, a power source, and two magnets to make a wire move perpendicular to a
magnetic field.
15. Sketch at least 6 positions of a compass around a magnet. [NOTE: the north end (Dark side) of compass must point in
direction of the south pole of the magnet!!]
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