Download AC/DC - Midland ISD

Electric current that repeatedly reverses
direction, twice each cycle. Usually at 60
cycles per second (or Hertz) in North
America…50 Hz elsewhere
The rate at which electrical energy is
converted into another form, such as light,
heat or mechanical energy
AC/DC

A battery produces
direct current b/c
the terminals always
have the same sign
What is the purpose
of the bolts on the
monster’s neck?

http://www.ehow.com/info_8080445_happen
s-jumper-cables-reversed-battery.html
Electrons always move through the circuit
in the same direction…from the repelling
negative terminal to the attracting positive
terminal



Remember…in the US we use primarily 120 v,
but 240 in dryers and stoves
We also use 60 Hz or 60 cyles/s
The popularity of A/C over D/C is
1) transmitted over greater distances (1 mi DC
between power plants, hundreds of mi A/C)
2) lower heat loss in wires

https://www.youtube.com/watch?v=knnhXMhXQ4
Electric Power = current x voltage
P
watts
=
I
x
V
= ampere x volt
1 kilowatt =
1000 watts
1 kilowatt-hour=
1 kilowatt
consumed in 1 hour
A 4-watt night light is plugged into a 120 v circuit
and operates continuously for 30 days.
a)
b)
c)
How much current does it draw?
How much resistance is in the filament?
What is the cost of its operation for the month
at the utility rate of 10 cents per kilowatt-hour?




A plasma tv draws 2 A when operated on 120
V.
How much power does the tv use?
If the tv is operated for an average of 7 hr/day,
what energy in kWh does it consume per
month (30 days)?
At 11¢ per kWh, what is the cost of operating
the tv per month?
A 6.0 V battery delivers a 0.50 A current to an
electrical motor. What power is consumed by the
motor?
P = IV
P = (0.50 A)(6.0 V)
P = 3.0 W