Transcript Let_s_Pivver_

Ohm’s Law
And Beyond
Let’s Pivver!!!
• What’s Pivver? Well, that’s not spelled
correctly. The correct spelling is:
P=IV and V=IR
• First, though, we’ll have to define some
terms.
Charge
• Electrons are negatively charged
particles that are responsible for the
flow of charge in an electric circuit.
• Electrons are so small and so many,
that we talk in terms of Coulombs (C).
• One coulomb is 6.25x1018 electrons.
• One electron has a charge of
–1.6x10-19 C.
What’s Charge?
(Click on the correct answer to this question below)
a. Charge is measured in Coulombs (C).
b. Electrons transfer charge through
wires.
c. One C is equal to 6.25x1018 electrons.
d. All of the above are true statements.
So Sorry, Try Again!
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Current
• Current is the flow of electrons through a
conductor (like a wire).
• The symbol for current is I.
• The unit for current is Amperes (Amps, or A).
• 1 A = 1 C/s, meaning one coulomb of
electrons flows past a point on a wire in one
second if there’s an Ampere of current
• Current = I = Amps = A = C/s
What’s Current?
(Click on the correct answer)
a.
b.
c.
d.
Current
Current
Current
Current
=
=
=
=
R = ohms = Ω = Js/C2.
I = Amps = A = C/s.
V = Volts = V = J/C.
P = Watts = W = J/s.
So Sorry, Try again!
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Voltage
• Voltage is the energy (Joules, or J) equivalent to the
potential work that could be done by two oppositely
charged plates (their attraction could move a mass).
• It’s also called potential, or potential difference. The
more difference in charge between the two plates,
the more work could be done, so the more equivalent
energy, the more push or pull, so the more voltage.
• The symbol for Voltage is V.
• The unit for voltage is Volts (V).
• Voltage = V = Volts = V = J/C
What’s Voltage?
(You know what to do)
a.
b.
c.
d.
Voltage
Voltage
Voltage
Voltage
=
=
=
=
R = ohms = Ω = Js/C2.
I = Amps = A = C/s.
V = Volts = V = J/C.
P = Watts = W = J/s.
So Sorry, Try again!
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Power
• Power is how much energy (J) is used
for a period of time (s) when using
electrical energy.
• The symbol for power is P.
• The unit for power is watts (W).
• Power = P = Watts = W = J/s.
What’s power?
a.
b.
c.
d.
Power
Power
Power
Power
=
=
=
=
R = ohms = Ω = Js/C2.
I = Amps = A = C/s.
V = Volts = V = J/C.
P = Watts = W = J/s.
So Sorry, Try again!
Click to try again
You’re Right!!!!
Keep Going!
Resistance
• Resistance is the resistance of a conductor’s (like a
wire) resistance to the flow of electrons.
• A type of friction, resistance creates heat in a wire,
and sometimes even makes the conductor glow
(think light bulb or electric stove).
• The symbol for resistance is R.
• The unit for resistance is ohms (Ω).
• Resistance = R = ohms = Ω = Js/C2
What’s resisistance?
a.
b.
c.
d.
Resistance
Resistance
Resistance
Resistance
=
=
=
=
R = ohms = Ω = Js/C2.
I = Amps = A = C/s.
V = Volts = V = J/C.
P = Watts = W = J/s.
So Sorry, Try again!
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Keep Going!
Resistance
opposes the
push
Voltage
supplies
the push
To Recap:
•
•
•
•
Current = I = Amps = A = C/s
Voltage = V = Volts = V = J/C
Power = P = Watts = W = J/s
Resistance = R = ohms = Ω = Js/C2
Current flow
results
Power is how
much energy is
used
Now Let’s Pivver!!!
Here are the equations you’ll need:
P = IV
V = IR
P = I2R
P = V2/R
Plus, you can rearrange them for any variable
you want! Free of Charge!
Let’s Pivver!!!
Here’s an example:
Your sister is using her 1500W hairdryer to dry
your hamster because she dropped it in her
piranah fish tank by accident and doesn’t
want you to find out. Your house has plugs
with 120V. What current does she draw using
the dryer?
Your sister is using her 1500W hairdryer to dry your hamster
because she dropped it in her piranah fish tank by accident and
doesn’t want you to find out. Her house has plugs with 120V. What
current does she draw using the dryer?
1. Decide which equation you need:
P = IV, V = IR, P = I2R, or P = V2/R?
I’ll say P = IV because it has all the relevant
variables, watts, volts, and amps.
2. Rearrange it for current:
I = P/V
3. Then put the given values in:
I = 1500W/120V = 12.5A
You try one:
What’s the resistance of a stove that is
using 20A and is plugged into 240V?
20A
R=?
240 V
What’s the resistance of a stove that is using 20A and is plugged
into 240V?
a.
b.
c.
d.
120 Ω
12 Ω
60 Ω
6Ω
So Sorry, Try again!
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OK, Just One More………
What’s the
power of a light
bulb on a 120V
circuit with
0.625A of
current runnung
through it?
What’s the power of a light bulb on a 120V circuit with
0.625A of current running through it?
a.
b.
c.
d.
45W
60W
100W
75W
So Sorry, Try again!
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You’re Right!!!!
Well, That’s All, Folks!!!
Remember, a
Pivver a day
keeps the short
circuits away!