DC (Direct Current)

•1831 Faraday devises the world’s first electric generator.

•As long as the rate was steady (not difficult to do), a continuous current is supplied to a load by this dc generator, or dynamo.

•DC goes one way, magnitude doesn’t vary (or varies only slightly).

Where is dc used?

•Really large electrical motors typically run on dc.•Ex: electric railway systems (like subways and

trolleys) typically run on dc.•Batteries

AC (Alternating Current)

•AC a current that reverses direction at regular intervals and varies in magnitude.

• Instead of having fixed polarity, the terminals in an ac generator alternate between +/- (always opposite of each other).

•The electrons that form a typical ac flow forward, then backward….essentially oscillating in place at some given number of cycles per second.

•AC is the dominant form of current.

AC vs. DC

Nikola Tesla VS. Thomas EdisonSerbian-American American

•Tesla created a practical ac induction motor that made ac far more appealing.

•Tesla was backed by industrialists championing high voltage ac (inc. General Electric) and faced off against low voltage dc (led by Edison).

Winner

Big factor?

•Power lines

•Higher voltage allows for a lower current to flow through the lines, resulting in less lost power.

•Transformer changes energy in the form of a large current and low voltage into nearly the same amount of energy in the form of a low current at a higher voltage.

•Step-up transformer voltage increased•Step-down transformer voltage decreased

• If the number of loops in the secondary coil is less than the number of loops in the primary, the voltage is stepped down.

• If the reverse is true, the voltage is stepped up.• (Vp/Vs)= (Np/Ns)