Download Electric Circuits and Electric Current

Electric Circuits and Electric
Current
PHYSICS SPRING 2015
Agenda 2/23/15
 Go Over Potential Test
 Retake Policy
 Debrief circuit building
 White board pictures of circuits
 Notes on Circuit Drawing
 Current analogy
 HW: Finish Current Analogy
White Boards
 Each person needs a white board and a maker
 Take no more than 30 seconds and draw…
 A circuit with a battery and a light bulb

A circuit with a battery and a toaster

A circuit with a battery, a light bulb, a hair dryer and a T.V.
The Physics Way
 In order to keep things consistent, we have a certain
way we draw each part of a circuit:
Try again…
 A circuit with a battery and a light bulb
 A circuit with a battery, a hair dryer and a T.V.
Agenda 2/23/15
 Circuit Warm Up
 Current Demo
 Current Notes
 Concept and Equation
 HW: Current Problems
On a sheet of paper
 Draw a circuit with three resistors and one battery
 Remember that these have specific symbols
Definition of Current
 Current:
 The flow of electrical charge per unit time
 Equation:
I = q/t
 Current is measured in units of AMPERES or amps
Example Problems
 In a current carrying wire, 3.0C of charge pass
through a given point every .02 seconds. What is the
current in this wire?
Example Problems
 The current through a copper wire is 12A. How
much charge will pass through a point in this wire in
a time of 10 seconds?
Example Problems
 An electron is traveling through a wire. One electron
passes through a point in the wire every .00500
seconds. What is the current in this wire?
Agenda 2/25/15
 Parts of a circuit warm-up
 Recap Current
 Discovering Ohm’s Law Lab
 Concept and Equation
 Notes on Ohm’s Law
 Ohm’s Law Practice problems
 HW: Complete Ohm’s Law Lab/Practice Problems
Warm-UP
 On a half sheet of paper answer these questions:
1.
2.
3.
4.
5.
How does a resistor effect the potential in a circuit?
How does a battery effect the potential in a circuit?
In terms of a battery, which end has high potential
and which end has a low potential
Which direction does charge flow? (think potential)
Which direction do electrons flow?
Add to notes
 Current: Flow of charge in a circuit.
 Flows from high potential (+) to low potential (-).
 Opposite the flow of electrons
 Battery: This provides the “push” of charge in a
circuit.

Takes lowered potential and raises it back to voltage of battery
 Resistance: Items in a circuit that reduce or slow the
flow of charge.

Lower the potential in the overall circuit
Warm-UP
 A wire is carrying a current. At a point in this wire
.001 C of charge passes through in 3 ms. What is the
magnitude of current in this wire?
Ohm’s Law Lab
 Safety:


Do not touch the resistors when the battery source is producing a
current.
When modifying the circuit always return the battery source to O
Volts.
 Tips:

When measuring current:
The red plug in the VΩmA hole and black plug in COM
 Dial should be turned to DCA 20m


When measuring voltage:
The red plug in VΩmA and black plug in COM
 Dial should be turned to DCV 20


Always have the red pin on the red end of the resistor and the black
end on the black end of the resistor
What is the resistance of your resistor?
Ohm’s Law
 An direct relationship between current and voltage.
 As voltage INCREASES current INCREASES (when resistance
stays the same)
 An indirect relationship between current and
resistance.

As resistance increases, current decreases (when voltage stays
the same)
 Equation:
V=IR
V= voltage (Volts)
I = current (Amps)
R= resistance (Ω, ohms)
Practice Problem
 What is the current in a circuit that has a power
supply of 12.0V and a resistor with a resistance of
100.0Ω?
Practice Problem
 What is the voltage of a battery if the current through
a circuit containing a 15Ω resistor is .300Amps?
Agenda 2/26/15
 Current/Resistance Warm-up

Review HW
 Recap Discovering Ohm’s Law

What relationships exist?
 Intro Power Lab
 Ohm’s Law Practice problems
 HW: Complete Ohm’s Problems, Get Power Meter
Reading
Practice Problem
 A circuit containing a battery and a resistor allows
.0015C of charge to pass through the resistor every
.010 ms. If the circuit is attached to a 9V battery,
what is the resistance in the resistor?
Discovering Ohm’s Law
 Let’s Recap
 What did we do in the lab yesterday?
 What did we measure?
 What was held constant?
 What shape did our graph take?
 What was our x variable?
 What was our y variable?
 What did the slope represent?
 What can we take away from this lab about the
relationship between V, I and R?
Power Lab
 Tomorrow we will discuss power.
 This weekend you are to explore the different
appliances you use in your house to determine how
much power you are consuming.
 Tonight it is your job to find out where the electrical
meter is and take a baseline reading. On Sunday you
will do the same to determine the overall
consumption of electrical energy you used this
weekend.
Agenda 2/27/15
 Check HW assignment

Initial if power reading taken
 Current and resistance exit slip
 Introduction Activity to Power

Physics Classroom
 Intro Power Lab
 Power Practice problems
 HW: Complete Power Lab Data table
Agenda 3/2/15
 Check Power Lab Data Table
 Discuss the mathematical portion of this lab
 Solve for energy usage and complete discussion questions
 Follow-up Activity (Going Green)
 Research viable alternatives
 HW: Complete a personal conclusion discussing the
changes you would make to your home.
Going Green
 Using a Chromebook:



Research viable alternatives to replace items in your home
Determine how much power and current these items draw
Determine how much money these items could save you over the
course of a year.

This research will be summarized in a personal conclusion that will
be turned in on Wednesday.

Conclusions should be long enough to clearly identify the changes
you are making and the reasons why you are making these changes.

**I will post this assignment to My Announcements on my d155
webiste
Agenda 3/4/15
 Collect Power Lab/Assignment
 Hand out equation sheets
 Power and Voltage warm-up
 Introduction to types of circuits
 Video Clip
 Ohm My Serious Lab
 Series Notes and Practice
 HW: Complete the Lab analysis questions
Warm-Up
 Complete #1-4 on the Power and Energy WS
 Check with a partner near you once you are complete
** Practice using your equation sheet
Types of Circuits
 The first type of circuit…the annoying circuit
 https://www.youtube.com/watch?v=rp8lwpvQEIM
 THE SERIES CIRCUIT
OHM My Seriously Lab
 Safety:
 Do not touch the alligator clips when the power supply is on.
 Only take measurements the way it is described in the lab.
 Tips:
 Keep the power supply at the same voltage during each setup.
 If you need to adjust wires, unplug the supply, don’t dial it down.
 Complete the three setups first and worry about the calculations
later.
**First determine the resistance in your resistors
What is the resistance of your resistor?
• The first two bands are digits
•The third band is the multiplier
Conclusions from the Series Lab
How is totally current affected?
1.

Total current is constant through each resistor
ITOT = I1 + I2 + I3 …
2. How is resistance of the whole circuit affected?

Total resistance is the sum of all resistors in series.
Req = RTOT = R 1 + R2 + R3 + …+ Rn
Agenda 3/5/15
 Warm-UP
 Series Circuit Lab

Revisit the Lab
 Notes on Series Circuits

Practice Problems
 VIR Tables
 HW: Complete the Series Practce
Warm-Up
 Complete #5-8 on the Power and Energy WS
 Don’t forget to use your equation sheet!!
Let’s Finish the lab
 Using your analysis from the lab:
1.
Calculate the Resistance and for each circuit.
2.
Answer the questions using the data on the following slide

The data goes in order of the lab and in order of increasing
number of resistors in a circuit.
One Resistor in Series
Resistor #
Manf.
Resistance
Current (I)
Voltage (V)
1
200
6A
1200V
Two Resistors in Series
Resistor #
Manf.
Resistance
Current (I)
Voltage (V)
1
200
3
560
2
240
3
690
Total
XXXXXXXXX
3
1250
Three Resistors in Series
Resistor #
Manf.
Resistance
Current (I)
Voltage (V)
1
200
2
385
2
240
2
500
3
390
2
785
Total
XXXXXXXXX
2
1700
Calculated
Resistance
Calculated
Resistance
Calculated
Resistance
One Resistor in Series
Resistor #
Manf.
Resistance
Current (I)
Voltage (V)
Calculated
Resistance
1
200
6A
1200V
200
Two Resistors in Series
Resistor #
Manf.
Resistance
Current (I)
Voltage (V)
Calculated
Resistance
1
200
3
560
186
2
240
3
690
225
Total
XXXXXXXXX
3
1250
416
Three Resistors in Series
Resistor #
Manf.
Resistance
Current (I)
Voltage (V)
Calculated
Resistance
1
200
2
385
192
2
240
2
500
250
3
390
2
785
393
Total
XXXXXXXXX
2
830
835
Conclusions from the Series Lab
How is total current affected?
1.

Total current is constant through each resistor.
ITOT = I1 = I2 = I3 …
2. How is the voltage affected in a the circuit?

The total voltage is the sum of all voltages in the circuit.
VTOT = V1 + V2 + V3 …
3. How is resistance of the whole circuit affected?

Total resistance is the sum of all resistors in series.
RTOT = R 1 + R2 + R3 + …
Conclusions from the Series Lab
 How does adding resistors affect the current?
 How does adding resistors affect the voltage?
 How does adding resistors affect the overall
resistance?
Let’s Practice
R
R1
10
R2
20
R3
30
Total
I
VIR TABLES
V
12V
Agenda 3/6/15
 Warm-UP
 Parallel Circuit Lab
 Findings from this lab
 Notes on Parallel Circuits
 Practice Problems
 VIR Tables: Parallel Circuits
 PhET Activity: Building circuits
 HW: Complete PhET
Conclusions from the Series Lab
 How does adding resistors affect the current?
 How does adding resistors affect the voltage?
 How does adding resistors affect the overall
resistance?
Let’s Finish the lab
 Using the data provided, complete the Ohm My,
Parallelouusly Lab and analysis.
One Resistor
Resistor #
Manf.
Resistance
Current (I)
Voltage (V)
Calculated
Resistance
1
200
6A
1200V
Two Resistors in Parallel
Resistor #
Manf.
Resistance
Current (I)
Voltage (V)
Calculated
Resistance
1
200
5.5A
1200V
218
2
240
4.9A
1200V
245
Total
XXXXXXXXX
11A
1200V
109
Three Resistors in Paralell
Resistor #
Manf.
Resistance
Current (I)
Voltage (V)
Calculated
Resistance
1
200
6.0A
1200V
200
2
240
5.1A
1200V
236
3
390
3.1A
1200V
387
Total
XXXXXXXXX
13.9A
1200V
86.3
One Resistor in Series
Resistor #
Manf.
Resistance
Current (I)
Voltage (V)
Calculated
Resistance
1
200
6A
1200V
200
Two Resistors in Series
Resistor #
Manf.
Resistance
Current (I)
Voltage (V)
Calculated
Resistance
1
200
3
560
186
2
240
3
690
225
Total
XXXXXXXXX
3
1250
416
Three Resistors in Series
Resistor #
Manf.
Resistance
Current (I)
Voltage (V)
Calculated
Resistance
1
200
2
385
192
2
240
2
500
250
3
390
2
785
393
Total
XXXXXXXXX
2
830
835
Conclusions from the Parallel Lab
How is total current calculated in parallel?
1.

Total current is the sum of current through each resistor.
ITOT = I1 + I2 + I3 …
2. How is total voltage calculated in parallel?

The total voltage is constant and equal to the battery’s voltage.
VTOT = V1 = V2 = V3 …
3. How is total resistance calculated in parallel?

The inverse of the total resistance is the sum of the inverse of
each resistor.
1/RTOT = 1/R 1 + 1/R2 + 1/R3 + …
Conclusions from the Parallel Lab
 How does adding resistors affect the total current?
 How does adding resistors affect the voltage?
 How does adding resistors affect the overall
resistance?
Let’s Practice
R
R1
10
R2
20
R3
30
Total
I
VIR TABLES
V
12V
Agenda 3/10/15
 Grab an Nspire
 Login to our network
 Complete the Circuit Activity
 Series and Parallel exit slip
 HW: None
Nspire info
 Settings
 Login
 Network 2
 Username: firsinitiallastname
 Example: sclause
 PW: lastname
 Example: clause
Agenda 3/11/15
 Review Lab Findings
 Turn in lab
 Nspire brainstorm and reflection
 Series and Parallel Exit Slip
 Combo Circuits Notes and Practice
 HW: Combo Circuits
 What kind of circuit is this?
Combo Circuit
 Let’s complete a VIR Table for the entire circuit.
R
BC
8
EF
3
GH
5
I
V
Parallel: EF and GH
DI
JK
Total
BC  DI JK: Series
6
12
Agenda 3/11/15
 Combo Circuit Warm-UP
 Hand back exit slips
 Nspire Review Questions
 Due by end of class for points
 HW: Complete the Review Guide for Circuits Unit
Combo Circuit
R
R1
10
R2
20
R3
30
I
V
R3,2
R1,2,3
Rtot
120