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Bell Ringer

Date post: 23-Feb-2016
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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?. Agenda. NOTES: Current Electric Static vs Current Voltage, Resistance, and Current Ohm’s Law. Current Electricity. - PowerPoint PPT Presentation
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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?
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Page 1: Bell Ringer

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?

Page 2: Bell Ringer

NOTES: Current ElectricStatic vs CurrentVoltage, Resistance, and CurrentOhm’s Law

Agenda

Page 3: Bell Ringer

Current ElectricityCurrent electricity is a steady flow of

electrons. Unlike static, current is always moving.

There are 3 characteristics of current electricity:VoltageCurrentResistance

Page 4: Bell Ringer

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)

Page 5: Bell Ringer

Pop Bottle Demo

Draw a picture and write a description of the demo with the pop bottles for voltage.

Page 6: Bell Ringer

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

Page 7: Bell Ringer

Pop Bottle Demo

Draw a picture and write a description of the demo with the pop bottles for current.

Page 8: Bell Ringer

2 Types of CurrentThere are 2 types of electrical

currentsDC = Direct CurrentAC = Alternating Current

Page 9: Bell Ringer

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.

Page 10: Bell Ringer

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!

Page 11: Bell Ringer

ResistanceOpposition to the flow of electronsUnit = Ohm (Ω)Symbol = R

• Highest resistance in:Poor conductors Thin wiresLong wires

Page 12: Bell Ringer

Ohm’s Law

V = I ● RVoltage (volts, V) Current

(amps, A)

Resistance(ohms, Ω)

•Relates Electric Current, Voltage, & Resistance

Page 13: Bell Ringer

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)

Page 14: Bell Ringer

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 = ___________

Page 15: Bell Ringer

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

Page 16: Bell Ringer

Assignments

Review questions and Ohm’s Law calculations


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