Alternating and Direct Current Direct Current (DC) is the one way flow of electrical charge from a positive to a negative charge. Batteries produce direct current. Direct Current is different than alternating current because the charge only flows in one direction. Alternating Current (AC) is when charges flow back and forth from a source. It is the way we receive our electricity (for our houses, businesses, etc.) The purpose of transformers is to convert AC voltages. Transformers are extremely important to AC current, and our life.

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? Due to the motion of the wire or magnet is converted to electrical energy

Electromagnetic induction & Generators Electromagnetic Induction 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.

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

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 Brain POP Sources of electricity:

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

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