Download Physics - cloudfront.net

Physics
Electricity
Review
• Circuits are fairly simple to solve, but only involve
MOVING charges.
• Remember the point charges we did the other day?
• If two charges q1 and q2 are 1 meter apart, and have
a charge of 1 Coulomb each, with what force will q1
push on q2?
Review…cont.
• 𝐹=
𝐾∗𝑞1∗𝑞2
𝑟2
• 𝐹=
• q1= 1C
• q2= 1C
• r= 1m
• K= 8.99*10^9
𝐾∗𝑞1∗𝑞2
𝑟2
𝑁𝑚2
∗1𝐶∗1𝐶
𝐶2
1𝑚2
8.99∗109
• =
• = 8.99*10^9 N of force. That’s
𝑁𝑚2
𝐶2
the equivalent of 1 billion pokes
at the same time. These forces
are huge! (That’s why we use tiny
point charges most of the time
Key Terms
•
•
•
•
Voltage
Current-Units are called amps
Ohm’s law
Power
Lesson Objective
• Students will be able to use Ohm’s law to determine
current and voltage in a system.
You will be successful if…
• If you can answer the questions on peardeck at the
end of the lesson.
Introduction
• Circuits carry charges from one place to another.
• If you picture a battery, there’s a positive end and a
negative end. When you attach them with a wire,
current flows from the negative side to the other
(positive).
• There is nothing to stop this flow or slow it down, so
as much electricity as possible rushes through from
positive side to negative side.
• This is where a Resistor comes in. It resist the flow,
much like a dam.
• Current is how much water flows through a river (in
our case how much electricity flows through the
wire)
• Voltage is how much pressure there is in the
current.
• Resistors slow the current down and reduce the
pressure (read current).
Fun video
This is how we draw a circuit
A circuit has 3
parts,
Voltage (V)
Current (I)
Resistance (R)
Scientist needed a
way to measure
the values in a
circuit, and so
they developed a
Ohms Law.
Heavy
• Ohms Law- 𝑉 = 𝐼𝑅
• This law allows us to find
how much current is
flowing through a wire at
any given point.
Heavy
• Lets solve one• If we have a circuit, and it
has 12 volts, for power, and
a 2Ω resistor, what is the
current flowing through the
circuit?
Example
• Ok, this time lets use the
Electric Eels voltage 500
volts.
• If your human body’s
resistance is .01Ω, how
much current went
through your body?
• Using Ohms law V=IR Plug in your known values.
• Given:
• V
• R
To find I adjust Ohms law to
Solve:
𝑉
𝑅
=𝐼
• Fun fact, why does an electric eel hurt so much…well…
• Lets use Power to measure it. A horse can apply a force of
750 Watts. We call it a horsepower, you might have heard of
it being used in cars.
• Multiply 𝑰 ∗ 𝑽 𝑡𝑜 𝑔𝑒𝑡 𝑷𝒐𝒘𝒆𝒓 𝑷
• Divide by 750 watts to get horsepower…How many horses
kicked you when you got shocked by the electric eel?
Check for understanding
Peardeck
Link to Haiku
Classwork