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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.
•
• q1= 1C
• q2= 1C
• r= 1m
• K= 8.99*10^9
•
• =
• = 8.99*10^9 N of force. That’s 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(Watch for these during the lesson.)
• 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 and interpret Ohm’s law to find missing parts of a circuit.
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.
Imagination time!(cuz electricity is hard to see in action)
• Current can be imagined as how much water flows through a river (in our case how much electricity flows through the wire).
• Voltage can be thought of as “how much pressure there is in the current.”
• Resistors slow the current down and reduce the pressure (read current slows down).
This is how we draw a circuit
A circuit has 3 parts, Voltage (V)Current (I)Resistance (R)
Scientist noticed the amount of current flowing in a circuit depended on how much resistance the circuit had. The only way to overcome this resistance was with more voltage (pressure).
Heavy
• Ohms Law-
• 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 resistor, what is the current flowing through the circuit?
• If we doubled the voltage, what might happen to the resistor?
• What about the current?
Try solving one on your own.
• Ok, this time lets use the Electric Eels voltage 600 volts.
• If your human body’s resistance is 1000.0, how much current went through your body?
Helpful hints:
• Using Ohms law V=IR Plug in your known values.
• Given: • V
• R
To find I adjust Ohms law to
Solve:
• Why would getting shocked by an electric eel hurt a lot?
Examine the following data
• Human body R=1000
• Electric Eel V= 600 volts
• A= .6 ampere (maximum value)
• If an electric eel was capable of putting out 1200 volts, what effect would this have on the current in the system? Why? (write a paragraph and explain, support your answer)
• What do can determine about the relation between resistance and current based on the above statement.