1. Producing Electric Current
Section 8.3: Physical Science

2. From Mechanical to Electrical Energy
A magnet can produce an electric current-
Moving a loop of wire through a magnetic field causes electric current to flow in the wire
Moving a magnet through a loop of wire has the same effect
How can a magnet produce a current in a wire?
ME due to the motion of the wire or magnet is converted to electrical energy

3. Electromagnetic induction & Generators
Producing an electric current by moving a loop of wire through a magnetic field or moving a magnet through a wire loop
Generators
Machines that produce electric current by rotating a coil of wire in a magnetic field
Wire coil is wrapped around an iron core and placed between the poles of a permanent magnet.

4. Generators Coil is rotated by an outside source of mechanical energy
Examples: Steam, wind, water
As the coil turns in the magnetic field, electric current flows through the wire
When the coil turns so that the ends move past opposite ends of the magnet:
The current reverses direction
The current changes direction twice with each revolution
A generator that is used in a car is known as an alternator

5. Electric Generators
Electricity in the home comes from a power plant with huge generators
When the coil is fixed and the magnet rotates, the current is the same as if the coil rotates and the magnet is fixed.
Construction of a generator in a power plant
Electromagnets contain coils of wire wrapped around iron cores
Rotating magnets connect to a turbine
Turbine: large wheel that rotates due to
Hoover Dam and Hydroelectric Power
Sources of electricity:

6. Direct and Alternating Currents
Compare and contrast current in batteries and generators:
Compare: Both devices move electrons through the wire
Contrast: Batteries have DC. Generators have AC.
DC- Direct Current- Flows in only one direction.
AC- Alternating current- reverses the direction of current flow regularly.
In N America, generators produce alternating current at a frequency of 60 cycles per second, or 60 Hz
A 60-Hz alternating current changes direction 120 times per second

7. Alternating Current

8. Transformers To make electric energy safe for your home you must:
Use a transformer- increases or decreases voltage
Transformers are made up of 2 coils (primary and scondary_ wrapped around an iron core.
Alternating current in a primary coil creates a changing magnetic field around the iron core, which induces an alternating current in the secondary coil

9. Transformers
Step – up transformer increases voltage. The secondary coil has more turns than the primary coil does
Step-down transformer decreases voltage. The secondary coil has fewer turns than the primary coil does

10. Electricity
Power carried in power lines as high as 750,000 volts is reduced by step-down transformers to household current (AC) of 120V
What happens to electrical energy as it passes through a wire?
Some is lost as heat due to resistance of the wire
Why is electrical energy transmitted at high voltages?
To prevent loss of energy as heat