Download Electricity in Your Home - St. John Paul II Collegiate

Electricity in Your Home
A power grid is a network that connects
electricity generating facilities,
transmission lines, distribution stations,
transformers, homes, and businesses.
In Canada the grid connects almost all
regions. As demand fluctuates, power is
regularly shifted from province to
province. Alberta might draw power from
BC during peak periods.
Read page 318
Transformers are used to:

Step up transformers are used to
increase the voltage. The purpose is
for efficient transmission of
electricity over long distances.

Step down transformers are used
to decrease the voltage. They are
found before the electricity enters
homes and businesses.
Read page 318-319
Activity on page 321.
Hand in your sample floor plan (#3), and a
sample room circuit diagram (#2).
Hand in #1 and #2 from “What did you
find out”
Read page 322.
The similarity between household circuits
and microelectronic circuits is that they
perform the same basic function: to
power an electrical device.
The main difference between household
circuits and microelectronic circuits is
the scale.
FYI – Transistors (on digital devices) act
as switches turning current on and off
and act as amplifiers increasing the
strength of an electric signal as it passes
through the transistor.
Microprocessing units (MPU) and CPUs
are large, complex circuits built on a tiny
piece of silicon. At their core are millions
of transistors connected by fine traces
of aluminum (conductors and pathways).
A MPU functions are dictated by
software that gives the chip its
instructions. Todays most advanced chips
contain more than 42 million transistors
and are continually becoming smaller and
smaller.
Measuring Electric Power
Power (P) -
the rate at which a device
converts energy.
- energy per unit time.
- Measured in watts.
There are two equations that describe
power relationships:
P = IV
E = Pt
Example:
A current of 13.6 A passes through an
electric baseboard heater when it is
connected to a 110 V wall outlet. What is
the power of the heater?
I = 13.6 A
V = 110 V
P = IV
= 13.6 X 110
= 1496 W
Example: How many joules of energy
does a 1200 W hair dryer use in 10
minutes each morning?
P = 1200 W
T = 10 mins or 600 seconds
E = Pt
= 1200 X 600sec
= 720 000 J
Example: A 100 W light bulb is plugged
into a 120 V outlet and is on for 5
minutes.
a)
What is the current?
P = 100 W
V = 120 V
T = 5 minutes = 300 seconds
P = IV
I=P/V
= 100 W / 120 V
= 0.83 A
b)
What is the energy used?
E = Pt
= 100 X 300sec
= 30 000 J
Work on questions #1-4 on page 324.
BLM 4-18
Read page 324  NOTE: Figure
4.47  a GOOD EXAM QUESTION
Given that 1 kW = 1000 W
1 hour = 60 minutes = 3600 seconds
kWh (kilowatt hours) =
kW (kilowatts) X
h (hours)
The cost of power ($) = kWh X $/kWh
See model problem on page 325.
On page 325 #1-3
BLM 4-19
BLM 4-20
Power rating – read page 326.
Almost all electrical devices are labeled
with their power rating or the number of
watts they consume every second they
are operating. If consumers know the
current rate per kWh that they are
paying for electricity, they can calculate
the amount of money they would save by
buying one brand over another.
Electrical Devices and Efficiency
Efficiency = useful energy output X 100
Total energy input
FYI  the efficiency of a car engine is
about 25%.
Go over the model problem on page 329.
On page 329 #1-3
BLM 4-22
Home Electric Safety
Read pages 330 – 331
Ways to reduce waste of energy in
common household devices:
- using more efficient forms of
lighting (halogen bulbs)
- pick energy efficient appliances
- don’t leave lights on
- use full loads of laundry and dishes
- add insulation around stoves,
windows, etc.
On page 331 #1-4