Generator and Transformer

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Transcript Generator and Transformer

Generator and
Transformer
Moving Conductor
If a straight conductor is moved in a
path perpendicular to a magnetic field, a
current is induced in the conductor
No current flows though since not a loop
Induced emf
=Blv
l – length of conductor
v – velocity of conductor
Example
An airplane travels at 1000 km/hr in
region where the Earth’s magnetic field
in 5.0 x 10-5 T. What is the emf induced
between the wing tips that are 70m
apart?
Generators (Dynamo)
Transforms mechanical energy into electric
energy
Coil of wire spins in the presence of a
permanent magnetic field
Induces are current in the coil
Current produced actually fluctuates as the
coils position in the field changes
Produces a current that switches direction
every half a rotation – Called Alternating
Current (AC)
Moving Electricity
How does electric energy transmit over
large distances?
Much less energy is lost when it travels
at a higher V and lower I
Transformer
Device that changes voltages
Two coils around an iron core
Current supplied to the primary coil
induces a current in the secondary coil
By varying the number of windings in
the coils you can vary the potentials
Equation
I P VS N S


I S VP N P
Types
Step-up – more windings on the
secondary coil increases the voltage
Step-down – less windings on the
secondary coil decreases the voltage
Transformers work only on AC current.
Why?
Transportation
Electric energy is stepped up for
transmission and then stepped down for
household use
Problem 1
A metal airplane with a wing span of 30m
flies horizontally at a constant speed of
320 km/h in a region where the Earth’s
magnetic field is 5.0 x 10-5 T. What is
the induced emf across its wing tips?
Problem 2
A 20 cm long metal rod is moving at a
speed of 10 m/s in a magnetic field of
0.30 T. Find
a) the induced emf in the rod
b) the current in the rod
Problem 3
An ideal transformer steps 8.0 V up to
2000 V, and the 4000 turn secondary
coil carries a current of 2.0 A. Find
a) the number of turns in the primary
coil.
b) the current in the primary coil
Problem 4
The primary coil of an ideal transformer
has 720 turns, and the secondary coil
has 180 turns. If the primary coil carries
15 A at a voltage of 120 V, for the
secondary coil what are the
a) voltage
b) current