Transcript Electromagnetic Induction

Electromagnetic Induction
A P R I L 4 TH 2 0 1 1
The Discovery
 In 1822, Michael Faraday wrote a goal in his
notebook: “Convert Magnetism into Electricity”.....
Nearly 10 years later he was able to demonstrate that
a changing magnetic field could produce an electric
current.
What is Electromagnetic Induction(EMI)?
 Current is produced in a conductor when it is moved
through a magnetic field because the magnetic lines
of force are applying a force on the electrons in the
conductor and causing them to move.

This process of generating current in a
conductor by placing the conductor in a changing
magnetic field is called induction.
 Electro Induction
What is EMI Cont.
 This is called induction because there is no
physical connection between the conductor and the
magnet.
 The conductor, which is often a piece of wire, must
be perpendicular to the magnetic lines of force in
order to produce the maximum force on the
electrons.
Direction of the Current
 The direction that the induced current flows is
determined by the direction of the lines of force and
by the direction the wire is moving in the field.
 To find the force charges in the wire, use the third
right hang rule; hold you right hand so that your
thumb points in the direction in which the wire is
moving and your fingers point in the direction of the
magnetic field. Your palm will point in the direction
of the current flow. (refer to diagram below)
Diagram
N
S
Electromotive Force
 Electromotive Force (EMF): it is the force that
makes electrons move in a certain direction within a
conductor.
 Even though it is called a force, it is a potential
difference and is measured in volts.
 If the moving wire is part of a close circuit, the EMF
will cause a current to flow in the direction of the
EMF.
Factors affects EMF
 The magnetic field – B (T)
 The length of the wire – L (m)
 The velocity of the wire in the field – v (m/s)
 Formula:
EMF = BLv
Ex. 1
 A straight wire 0.20m long move perpendicularly
through a magnetic field induction of 8.0x 10 -2 T at a
speed of 7.0m/s. a. What EMF is induced on the
wire? b. The wire is part of a circuit that has a
resistance of 0.50Ω, what current flows in the
circuit?
L = 0.20m, B = 8.0x 10 -2 T , v = 7.0m/s,
R = 0.50 Ω
Solution.
a) EMF = BLv
= (8.0x 10 -2 T) (0.20m) (7.0m/s)
= (8.0x 10 -2 N/Am) (0.20m) (7.0m/s)
= 0.11 (N/Am)(m)(m/s)
= 0.11 W/A
= 0.11 V
b) I = V/R
= (0.11V/0.50Ω)
= 0.22A
Homework.
 Pg. 796 # 1-4, 6
 Pg 799 20