Transcript Slide 1 - hsheldon

What do you know about electricity that goes through
wires? Tell me everything you can.
Notes on Electric Current
Flow of
charge
notes
Imagine we have the charges below.
We place a light bulb nearby. If we place
an electron somewhere, can we get it to
“flow” through the light bulb?
Notes on Electric Current
Flow of
charge
Imagine we have the charges below.
We place a light bulb nearby. If we place
an electron somewhere, can we get it to
“flow” through the light bulb?
Maybe, but it would be hard. There are a
lot of ways our electron can go from
positive to negative.
Notes on Electric Current
Flow of
charge
Imagine we have the charges below.
We place a light bulb nearby. If we place
an electron somewhere, can we get it to
“flow” through the light bulb?
Maybe, but it would be hard. There are a
lot of ways our electron can go from
positive to negative
If we add a wire, we can force the
electron to flow how we want!
Notes on Electric Current
Flow of
charge
This idea is electric current.
Confusing? This of this like water.
Water will flow downhill, but it can do so
in may ways. If we put it in a pipe, we
can direct where it flows.
is a
lot
like
Notes on Electric Current
Current and
amperage
This flow of electrons is called electric
current. We can measure how fast this
flows. We call this rate amperage.
1 amp = 1 coulomb / second.
The unit for current is “A”.
Notes on Electric Current
Current and
amperage
This flow of electrons is called electric
current. We can measure how fast this
flows. We call this rate amperage.
1 amp = 1 coulomb / second.
The unit for current is “A”.
In the pipe analogy, think of current as
how much water flows through a section
of pipe each second.
High flowrate =
High current!
Big wire=more current
Notes on Electric Current
Batteries and
voltage
Electrons will stop flowing once they run
out of electric potential, just like water
stops flowing once it’s reached ground.
=
=
Notes on Electric Current
Batteries and
voltage
Electrons will stop flowing once they run
out of electric potential, just like water
stops flowing once it’s reached ground.
=
=
The job of a battery is to pull the electrons
from the positive charge and put them back
on the negative charge, restoring the
potential difference.
Just like how a pump can bring water back
up to a higher point so it can flow again.
Notes on Electric Current
Batteries and
voltage
Batteries are all about restoring electric
potential. How do we measure electric
potential?
Notes on Electric Current
Batteries and
voltage
Batteries are all about restoring electric
potential. How do we measure electric
potential?
In volts! Before we said volts are how
much energy each charge holds. In
circuits, this represents pressure. The
more voltage a battery has, the more
pressure for electrons to flow.
In our pipe analogy, the higher up the
water gets, the more it pushes to flow
down.
Notes on Electric Current
Resistance
As electrons try to flow from high
potential to low potential they may
encounter things that slow them down.
In the pipe analogy, this could
be like a blockage in the pipe.
The water still flows through,
but it takes a bit of work and
the pressure will go down.
Notes on Electric Current
Resistance
As electrons try to flow from high
potential to low potential they may
encounter things that slow them down.
In the pipe analogy, this could
be like a blockage in the pipe.
The water still flows through,
but it takes a bit of work and
the pressure will go down.
In circuits, resistance is measured in
ohms.
The unit for resistance is Ω.
Notes on Electric Current
Resistance
It’s important know that electricity – just
like flowing water – will take the path of
least resistance.
Electrons flow through the wire because
the wire is easier to flow through than the
ground or air. Both have a very high
resistance.
Keep this in mind!
Notes on Electric Current
Electric
Shock
When you feel a shock, which is it that
kills you: the current or the voltage?
Notes on Electric Current
Electric
Shock
When you feel a shock, which is it that
kills you: the current or the voltage?
Current! It’s the number of electrons, not
the pressure behind them that kills.
Wet skin offers less resistance than dry
skin. Less resistance means more current.
More current means more electrons!
A current of 0.1 A can be enough to kill.
equations
Equations
Ohm’s Law
V = I•R
OR
V
I
R
V: Voltage (Measured in volts)
I: Current (Measured in amperes)
R: Resistance (Measured in ohms)
Use this equation to find voltage,
current, or resistance for any circuit
with 1 resistor.
(to use the diagram, cover up what
you want and do what’s shown to get
it)
vocab
Vocabulary
Electric Current
The flow of electric charge.
Amperage
The volume of electrons flowing past at
any one time.
Voltage
(circuits)
The amount of energy pushing the
electrons around the circuit. (Like
pressure)
Resistance
How much the flow of electrons is slowed.
Exit Question #9
What's the difference between current and voltage?
a)
b)
c)
d)
e)
f)
current
current
current
current
current
current
is
is
is
is
is
is
like
like
like
like
like
like
volume, voltage is like pressure
pressure, voltage is like volume
speed, voltage is like pressure
pressure, voltage is like speed
volume, voltage is like speed
speed, voltage is like volume