Power and Energy notes
What do the atoms in a
wire look like?
What particles move in
an electric circuit?
What do we call the total
amount of charge that
passes a point each
second in an electric
circuit?
What is the current in a
circuit where 1 coulomb
of charges pass a point
each second?
___________ are the things that
move in an electric circuit
Current
The amount of ________ (number of
electrons) that pass a point in a given
________ is called _________
(symbol is I). Instead of individual
electrons passing a point we talk
about a group of electrons, 6.25 x
1018 or _________ of charge passing
a point in a wire.
If one _________ of charge passes a
point in one _________ then you
have 1 C/s of current …AKA… one
_________ (1 A)
I = q/t
Which is constant for an
electron: the charge or
the energy it carries?
The _________ of an electron never
changes but the _________ they
carry can change
A)
e-
B)
e-
C)
e-
eee-
Which of the pairs of
electrons has the most
charge?
________, the charges on the
electrons are ___________.
Which of the pairs of
electrons has the most
stored energy?
The electrons that are the _________
__________, ___.
What is the amount of
energy per coulomb of
charges called?
Voltage
The amount of _______ per
_____________ of charges is called
______________.
V= E/q
Energy per charge would be
measured in Joules/Coulomb …
J/C… AKA… ________ (__).
What is the voltage of a
standard AA battery? A
standard AAA battery?
AAA, AA, C and D batteries are all
_____ _______. 9V batteries are
made from 6-1.5 volt batteries linked
together in series.
Notes on power
Electrical devices need a certain
amount of _________ each
___________ to operate.
What is the amount of
energy needed per
second called? What are
the units?
The amount of _______ needed each
_________ to operate is called
________ and is measured in
_______.
What is a Watt equal to?
One Watt (W) is equal to One
________ of ________ per
_________. (J/s)
What is the equation to
find power?
P=IV
P
I
EXAMPLE 1 - A circuit
consists of a 12 volt
battery creating a current
of 3.0 amps. Determine
the power supplied by
the battery.
EXAMPLE 2 – A 45 W
circuit has 27 J of energy
for every 3 C of charge.
Determine the amount of
charge that passes a
point in the circuit every
5 seconds.
V
Notes on energy
How can power be used to
find total energy?
___________ indicates how much
________ is used in a given ______, to
find the total energy used to operate a
device we need to multiply ________ by
the ________ of operation.
E=Pt
E
P
If power is in Watts and
time in seconds, what is the
unit for energy used?
t
If power is in Watts (J/s) and time is in
seconds, when we multiply to find energy
used the unit will be _______. This can
lead to very large numbers for devices that
are used for long periods of time or require
large power.
How much energy in Joules
is used by a 1000 W water
heater on for one hour?
If power is in kW and time
in hours, what is the unit for
energy used?
How much energy in kWh is
used by the 1000 W water
heater on for one hour?
Another way to find energy used, as the
power company does and as we will in this
class on the HFE project, is in ______.
For this, the ________ is changed from W
to kW by dividing by _____. The power
in kW is then multiplied by time in hours.
This leads to smaller answers for energy
that can be better understood.