Bell Ringer
You walk up to your friend to give him a high-five for acing his science test. To your surprise, you shock him instead. Why did this happen?
NOTES: Current ElectricStatic vs CurrentVoltage, Resistance, and CurrentOhm’s Law
Agenda
Current ElectricityCurrent electricity is a steady flow of
electrons. Unlike static, current is always moving.
There are 3 characteristics of current electricity:VoltageCurrentResistance
Voltage (Potential Difference)
The PUSH that makes electrons flow (electrons have potential to flow but won’t on their own)
A difference between energy levels is needed for flow• Electrons flow in a circuit when there is an
energy difference from one end of the energy source to the other end of the energy source (like a battery)
Units = VOLTS (V) 1 Volt = 1 Joule/Coulomb
Symbol = V (capital)
Pop Bottle Demo
Draw a picture and write a description of the demo with the pop bottles for voltage.
Electric CurrentThe FLOW of electric charges in a circuitUnits = Amperes (amps)
1 amp = 1 C/s (1 Coulomb of charge moving past a point in 1 second)
Symbol = ISpeed of Current is affected by
• Type, length, & thickness of wire• Voltage
When Voltage , Current
Pop Bottle Demo
Draw a picture and write a description of the demo with the pop bottles for current.
2 Types of CurrentThere are 2 types of electrical
currentsDC = Direct CurrentAC = Alternating Current
DC electricityDirect current means that
the electrons flow in only one direction.
This is the kind of electricity produced by a battery
Electrons come out of the negative end and flow back into the positive end.
AC electricityAlternating Current electricity means that
the direction of electron flow flips back and forth
This is the kind of electricity produced by spinning a generator.
The electricity in homes in the United States changes direction 60 times a second!
ResistanceOpposition to the flow of electronsUnit = Ohm (Ω)Symbol = R
• Highest resistance in:Poor conductors Thin wiresLong wires
Ohm’s Law
V = I ● RVoltage (volts, V) Current
(amps, A)
Resistance(ohms, Ω)
•Relates Electric Current, Voltage, & Resistance
Practice Problem 1
Calculate the voltage across a 3Ω resistor if a 0.5 amp current is flowing through it.
V = ___________
I = ____________
R = ___________
V = I ● RV = 0.5 amps x 3 ohm’sV = 1.5 volts
?0.5 amps
3 Ω (ohm’s)
Practice Problem 2
A radio with a resistance of 240 Ω is plugged into a 120 V outlet. What is the current flowing through the outlet?
V = I ● R120 V = I ● 240 ΩI = 120 V
240 Ω
120 V
?240 Ω
I = 0.5 amps
V = ___________
I = ____________
R = ___________
Practice Problem 3
Find the resistance of a circuit that draws 0.06 amps with 12 volts applied.
V = ___________
I = ____________
R = ___________
V = I ● R12 v = 0.06 amps ● RR = 12 V
0.06 amps
12 V
0.06 amps
?
R = 200 Ω
Assignments
Review questions and Ohm’s Law calculations