Transcript ELECTROMAGNETISM - Illinois Institute of Technology

ELECTROMAGNETISM
LAB RESULTS
• CIRCUIT LAB – a compass needle
deflected when placed near the circuit. WHY?
• ELECTROMAGNETIC INDUCTION LAB
• Moving magnets result in current
• The size of the induced current(as read on the galvanometer) was
bigger when we
1. Used a stronger magnet.
2. Moved the magnet at a faster speed.
3. Used more turns of wire on the coil.
• WHY?
ANSWER TO CIRCUIT LAB
CURRENT INDUCES A
MAGNETIC FIELD
• Current running through a
conductor will produce a
magnetic field
MAGNETIC FORCE
• A conductor that has current running
through it, will also have a magnetic field
surrounding it
• If this conductor is placed within the
vicinity of ANOTHER magnetic field, the
two fields influence on another via a
magnetic force
MAGNETIC FIELD FOR LONG
STRAIGHT WIRE
• B = Fmax / IL
• B = magnetic field in tesla
• F = maximum value of force on wire in
newtons
• I = current in amperes
• L = length of wire in meters
Direction of Magnetic Field
You can work out the direction of the field using your right
clenched fist.
Point your thumb upwards in the same direction as the
current.
The direction of the field is the same direction in which
your fingers curl.
gcsescience.com
SAMPLE PROBLEM
• The force on a wire carrying 30.0A is a
maximum of 3.80 N when placed between
the pole faces of a magnet. If the pole
faces are 25.0 cm in diameter, what is the
strength of the magnetic field?
SOULTION
• B = Fmax / IL
• B = 3.80N/30.0A( .250meters)
• .507 Tesla
MAGNETIC FORCE
• B = Fmax / IL
• BIL = Fmax
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B( q/t) L = Fmax
B(qL/t) = Fmax
B(q)(L/t) = Fmax
Bqv = Fmax
MAGNETIC FORCE
Fmag = qvBsin ө
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Where q is the amount of charge
v is the velocity of the particle
B is the magnetic field
ө the angle formed between the velocity
and magnetic field directions.
•
http://solar-center.stanford.edu/magnetism/magneticforce.html
RIGHT HAND RULE
Right thumb points in the direction of the current. Your fingers, all point in the
direction of the field. Your palm will then be in the direction of the magnetic force.
http://www.waukesha.k12.wi.us/South/physics1/2.6/RHrule3.jpg
SAMPLE PROBLEM
• Determine the magnitude and direction of
the force on a proton traveling in a vacuum
tube at 2.84 x 105 m/s horizontally to the
east in a vertically upward magnetic field
of strength 1.60 T.
SOLUTION
Fmag = qvBsin ө
• F = 1.6 x 10-19C(2.84 x 105 m/s )(1.60T)sin 90
• 7.27x 10-14 N
• Direction – use right hand rule for force
• Direction – out of paper or south
ANSWER TO
ELECTROMAGNETIC
INDUCTION LAB
INDUCED CURRENT
• Just as a current flowing through a wire
will produce a magnetic field,
likewise a moving magnetic field
near a stationary wire will produce a
current flowing through the wire.
This is called induced current.
• gcsescience.com
Induced Current in a Coil.
When a magnet is moved towards and inside a coil of wire,
a current is induced inside the wire.
gcsescience.com
INDUCED emf
• In order for an induced
current to be generatedyou must first have an
induced electromotive force
A conductor near a moving magnetic field
experiences separation of positive and
negative charges within the conductor. This
leads to an induced EMF across the
conductor
http://bama.ua.edu/~calexand/PH102/labs/ind.htm
INDUCED EMF
• Ε = Blv
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Ε= induced emf in volts
B = magnetic field in tesla
L = length of conductor in meters
V= velocity of field relative to conductor
(m/s)
PRACTICE PROBLEM
• A bar of length 10 cm slides along metal
rails at a speed of 5 m/s in a magnetic field
of 0.1 T. What is the motional emf induced
in the bar and rails?
SOLUTION
• Emf= Blv
• Emf = .1T(.1m)(5m/s)
Emf = 5 x 10-2 V