Transcript Electrical Circuits

Warm-up Activity
• Think about your experience with the PhET
circuit simulation that you recently
completed
• Record in your notebook:
– Two things that you enjoyed/learned from the
lab
– One thing that you feel you didn’t understand
• Discuss your responses with your group
members
Electrical Power & Energy
Electrical Energy
• Most electrical energy is produced from
natural resources and provided to our homes
by Electrical Utility Companies.
How does the electrical company
produce energy?
Circuits
(energy transformation tools)
• Circuits are a way to convert electrical
energy into energy we need such as heat
and light.
Electrical Power
The rate at which the electrical energy is converted
into useful energy such as heat or light (depends
on the device).
This light
bulb takes
60 Joules
of energy
from the
circuit
every
second!
60 Watts
100 Watts
This light
bulb takes
100 Joules
of energy
from the
circuit
every
second!
Electrical Power
P = IV
Power (Watts)
Current (Amps)
Voltage (Volts)
Example
A lamp operates with a current of .83 A and
a potential difference of 120 V. How much
power does the lamp use?
Electrical Energy
• Amount of energy used depends upon
power requirements by appliances and how
long they are used
E = Pt
Energy (kWh)
(J)
Power (kW)
(W)
Time (hrs)
(s)
Household Circuits
• Standard voltage in U.S. 120V
• Main switch and circuit breaker box serve
as “electrical headquarters” for your home
• Many appliances can draw current from the
same circuit. A fuse or circuit breaker is
wired in between each parallel circuit.
Electrical Energy Problem
A 60 W lightbulb is left on for 8.5 hours.
How many kWh of energy are used? How
many Joules of energy are used?
Assume Xcel energy charges $.10 per kWh (or per
3,600,000 Joules). How much would it cost to run
the lightbulb in the previous question for one week
(assuming it was on 8.5 hrs/day)
Electrical Safety
• Correct wiring, fuses, circuit breakers,
insulation and grounded plugs help make
electrical energy safe
Energy in your home
• Draw on your personal experiences to
calculate your family’s energy usage!
• Think of a normal week when all members
of your family are home
• Determine how many hours each appliance
is actually used
• If there is more than one of the same type of
appliance in your house, count all of them
toward your total!
A scent plug in uses 120 V of potential
difference and a current of 1.1. A to
operate. How much power is the scent
plug-in using?
1.
2.
3.
4.
109.1 W
132 W
121.1 W
Not enough
information
25%
1
25%
25%
2
3
25%
4
If the scent plug in has a power rating
of 132 W, what is the power in kW?
25%
1.
2.
3.
4.
25%
25%
2
3
25%
132000 kW
13.2 kW
0.132 kW
0.000132 kW
1
4
If the scent plug in uses 0.132 kW of power
and is plugged in at all times, how many
kilowatt-hours of Energy are used in 1 week?
25%
1.
2.
3.
4.
25%
25%
2
3
25%
22.18 kWh
3.168 kWh
1272.7 kWh
Less than 1 kWh
1
4
If the energy company charges $0.10 for
every kWh of energy used, how much would
you be chared for 22.18 kWh of usage?
25%
1.
2.
3.
4.
25%
25%
2
3
25%
$0.79
$1.50
$221.80
$2.22
1
4
Are the Vikings going to beat the
Packers tomorrow?
1.
2.
3.
4.
5.
6.
Definitely
Yes
Most Definitely
No
Guaranteed
Yes
17%
1
17%
2
17%
17%
3
4
17%
5
17%
6