Electric Circuits

Potential Electric Potential is just like gravitational potential It depends on –The distance from the source –The amount of charge

Potential Difference When there is a potential difference, charge flows from the higher potential to the lower potential The greater the potential difference, the more charge that can flow –Gravitational Example

More Potential Difference We call this potential difference Voltage –Means electric potential energy per charge Measured in Volts or V

Electric Circuits For charge to flow, there must be –A place to get charge from –A place for the charge to go In other words, there must be a “loop” or complete path for the electrons to travel

More Circuits Basically, circuits must follow two requirements: –There must be an energy supply (like a battery) creating a potential difference –There must be a closed, conducting loop that connects the high potential to the low potential Hint: You’ll need to know these for the test!

Current Current: The amount of charge that flows per given time Measured in Amperes 1 A = 1 C/s

Resistance Resistance determines how much current will flow –Measured in Ohms or Ω Think of this as a sort of “current limiter”, BUT voltage drops across a resistor

More Current The amount of charge that can flow is related to how much resistance to flow there is –If resistance goes up, current goes down –If potential difference goes up, current goes up

Ohm’s Law Resistance = Voltage/Current R = V / I Also written V = IR And I = V / R

Power Power is still measured in Watts (or W) Power in a circuit is written as the following:

More POWER! Power can be written in different ways as well using Ohm’s Law!

Analogy to Water astr.gsu.edu/hbase/electric/watcir.html

Whiteboard Problems A 30V battery maintains current through a 10 Ω resistor. –What is the current? –What is the power? An automobile headlight with a resistance of 30 Ω is placed across a 12V battery. –What is the current? –What is the power?

More! A radio uses 2x10 -4 A of current when operated by a 3V battery. –What is the resistance of the radio? –What is the power?