Generator and Transformer

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Transcript Generator and Transformer

Generator and
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
l – length of conductor
v – velocity of conductor
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
Generators (Dynamo)
Transforms mechanical energy into electric
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
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
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.
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
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