FarleyPhysics.com

Ohm’s Law Notes (Page 6)

Use the following simulationto study “Ohm’s Law”:

1. Raise the voltage until you have 9V.  How many 1.5 V batteries does it take?  Take a picture of this with Command-Shift-4.

2. Decrease the Amount of batteries and come up with a rule for how the number of batteries effect the Voltage in the circuit.

3. As you increase the Voltage, what happens to the current?  Take a picture with Command-shift-4.

4. As you decrease the Voltage, what happens to the current?

5. As you increase the resistance, what happens to the current?  Take a picture with Command-shift-4

6. As you decrease the resistance, what happens to the current?

Use the circuit construction kit here  to create all six circuits on the board.

1. You need to right-click or Control-Click to change the resistance of the light to the proper value.

2. Set up a voltmeter across the light or lights, and an ammeter somewhere in the circuit.

3. Take a picture of each circuit with Command-Shift-4 and put your circuit in a comic.

Create a ten square comic with these images as well as captions explaining what is important in each picture and what the picture shows.  Title it “Ohm’s Law”

Today we study resistance.  Resistance is a measure of a materials ability to resist the flow of electricity.  Everything from a wire, to a light, to a motor, to an actual resistor has resistance.  Everything but a superconductor.

Use this simulation to learn about resistance.

“Battery-Resistor”:

Check “show inside battery” and “show cores”, watch what happens, adjust some variables and play a little.

1. Why do electrons (blue dots) move? What’s pushing them?  Draw a diagram of the battery, label the flow of electrons.

2. What does the Ammeter (on the left) measure? How is this shown in the sim?

3. What role do the “green dots” in the resistor play in the sim? What do you think they represent?  How do they change as you turn the resistance up and down?

4. Increase the resistance (# green dots). What affect does this have on temperature? WHY?

5. To make the circuit “cold”, what do you need to do? WHY?

6. Describe the relationship between voltage and temperature.

Use the following simulation: “Resistance in a Wire”

1. In this sim, R is the resistance, rho (ρ) is the resistivity, L is the length of the wire, and A is the cross sectional area (thickness) of the wire.  Write down the formula in your notes and write down what each variable stands for.

2. Try increasing the resistivity (ρ) of the resistor. What changes in the resistor?

3. Now increase the length (L). What happens to “R”? WHY?

4. Now increase the area (A) of the resistor. What changes? WHY?

5. Write a summary about the different relationships you looked at in the properties and measurements of a resistor.

Use the following simulationto study “Ohm’s Law”:

In this sim, vary the values of Resistance (R), Current (I) and Voltage (V).

1. Find  three different combinations of V and R which get a current (I) of 6 mA  (milliamps)?

2. Describe the relationship between I and R. Why is this?

3. What would happen to the current if you could decrease the resistance to 0? Explain why in terms of resistance and the flow of electricity.

Voltage is the electrical equivalent to potential energy.  If you think of a bunch of charges on top of a building, they have the ability to do work (make heat and light), but they need a path to get down.  Electrons get down by going through a light, a resistor, or a motor.

To understand voltage in a circuit, construct the following circuit:

Click the box to create a voltmeter and use the two electrodes to test the voltage of your battery.
 Then test the voltage across the light.  Be sure to keep the electrodes in the order they are in the image below:

1. Draw the circuit and label the voltage across the battery and across the light.

Now add a light to the circuit like this:

2.  Draw the circuit in your notes, measure the voltages across the battery and each of the lights, and label the voltages across each light.

3. How do the voltages across each light compare to the voltage across the battery?

4. Add another light and test the voltages.  These lights in a row are what’s called a “SERIES” circuit, because each light is in series.  Write a statement explaining how voltage changes in a series circuit.

Now you will create what is called a “PARALLEL” circuit and test its voltages.  Make this circuit:
5. Measure the voltage across the battery and each light.  Be sure to keep the red electrode on the top and the black on the bottom. Draw the circuit and label the voltages.

6. Add another light, draw the circuit, and label the voltages.

7. How do voltages change in a parallel circuit?

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Return and go over quizzes.

Run the simulation here, draw it in your notes, and answer the following questions:

1. What is the current through the circuit when the battery voltage is zero?

2. What happens to the current as voltage increases?

3. Write what you found in #2 as a rule or a statement about voltage and current.

Run the Circuit Construction Kit here.

4. Create a circuit like this one and draw it in your notes.

Create a Non-Contact Ammeter by clicking the box in the tools section.

Put the Ammeter over a wire and measure the current through the wire.

5. Move the ammeter to another wire and all around your circuit.  Label each wire with the current that is going through it.

6. What you have just found is called “Kirchhoff Law.”  Look it up and explain how it applies to your circuit and what you found.

7. Add another light like this:

8.  Measure the amperage around the circuit.  Complete this sentence: Twice the lights gives you ___________ the current through the circuit.

9. Add another light and write a similar sentence to #6.

10. Delete the lights and replace them with resistors.  Do resistors work the same way as lights?  What’s the difference?

11. Create a circuit like the following circuit:
Draw the circuit in your notes and measure the current through each wire.  Label each wire with the current going through it.

12. How does the current split when it has two paths to go through?

13. How does the current split when it has three paths to go through?

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Find the answers to these questions in your notes and be sure you know them.  Write each question and answer or write the answer as a complete sentence.  Pages 1-8 of your notes are due tomorrow.

1. Opposite charges… (attract or repel)

2. Like charges… (attract or repel)

3. Draw the electric field from a positive charge.  Show the direction of the field with arrows.

4. Draw the electric field from a negative charge. Show the direction of the field with arrows.

5. A positive charge placed in an electric field, will have a force on it in what direction?

6. If a balloon is rubbed up against a sweater, what part of the atom is transferred to the balloon?

7. If a balloon is rubbed up against a sweater, the sweater becomes charged… (positively or negatively)

8. What is it called when charge is moved by rubbing?

9. Iridium (Ir #77) has how many protons, how many neutrons, and how many electrons in a stable, neutral atom?  Periodic Chart.

10. The element with a single proton in the nucleus is called?

11. Every atom of carbon was created where?

12. Gold and other heavy elements were created where?

13. What makes an electrically neutral atom?

14. What is an ion?

15. What is the charge of a neutron?

16. List 3 everyday examples of static electricity.

17. What are the charged parts of the atom?

18. What is the unit of charge?

19. What is the charge on one electron?

20. If a charge has 4 field lines coming out of it, and another charge has eight field lines going into it.  What can you say about the two charges?

Go Here and answer the following questions in your notebook as you read:
1. List 3 everyday experiences having to do with Static Electricity.
2. Describe the atom model suggested by J.J. Thompson.
3. What was Rutherford’s model of the atom?
4. What was Neils Bohr’s improvement on Rutherford’s atom?
5. Describe the Quantum Mechanical description of the atom and draw a picture of it.
6. List the properties of the proton, the neutron, and the electron.
7. Answer the question at the bottom of the page.

Go to the next section and answer the following questions:
9. How do you create an electrically neutral atom?
10. What is an Ion?
11. List three common examples where electrons move from one material into another.
12. What is the unit of charge?
13. What is the charge of an electron?

1. Protons, Neutrons, Nucleus, Electrons notes (page 5)

Periodic Square Comic Assignment.

Create a six square comic.

Square 1: Title is “Atoms”

1. Go to the photographic periodic table here.  It’s the coolest Periodic Table around.

Square 2: Pick an element and click on it.  Copy the periodic square.  In the bubble, state how many protons and neutrons are in the atom.  In a little text box, put something the atom is useful for or something special about it.

Square 3 and 4: To the same for two more atoms.

Build an atom squares:

Squares 5 and 6:

1. Use the following simulation to build 2 stable and neutral atoms.

2. Create a Helium atom, and one more of your choice.

3. For each atom you make, create a square in your comic.  The text should state the number of protons, neutrons, and electrons in the neutral atom and some fact about the element.

Print it and put it in your notes!