California Standard Addressed
5. Electric and magnetic phenomena are related and have many practical applications. As a basis for understanding this concept:
5.a. Students know how to predict the voltage or current in simple direct current (DC) electric circuits constructed from batteries, wires, resistors, and capacitors.
SDUSD Student Performance Outcomes
Identify and define a voltage source within a simple circuit.
Identify a path for the movement of charge in a simple circuit.
Summarize why charge moves in a simple circuit.
Define current in an electric circuit. / Name
Date
Period
Engage
/ Record your responses to these questions in your lab journal.1. How does a light bulb work?
2. Draw arrows on the diagram or any other marks to help explain how the light bulb works.
3. Imagine that you are given a bulb, a battery and a wire segment.
How would you connect the wire and the battery to get the light bulb to glow?
Draw as many working set ups as you can.
Share your responses with your lab group members. Develop a consensus around the best answers for these questions. Share your ideas with the class.
Explore
The teacher will provide your group with a battery, bulb and wire segment.
Experiment with these materials until you discover at least two different ways to arrange these materials to make the light bulb glow.
4. Carefully diagram successful arrangements.
5. Compare your predictions in the ENGAGE to the evidence. Were your ideas supported by the evidence or has your thinking changed?
6. What general conditions have to be true for the light bulb to light?
Explain
7. A complete loop or path from one end of a battery to the other is referred to as a circuit. An open circuit is one that is not complete and has a gap or separation between one end of the battery and the other. A closed circuit is one that has a complete uninterrupted path from one end of the battery to the other. Which of the following is a closed circuit?
AB
8. Examine your diagrams of working wire, battery and light bulb arrangements. Are they open or closed circuits?
9. Examine the diagrams below. Indicate which diagrams are closed circuits.
10. Will the closed circuits you selected in 9. result in a light bulb that glows?
Examine the drawing on the right. Imagine that you give the ball a small push at the top of the smooth hill.11. Predict what will happen to the velocity of the ball as it approaches point B? Why?
(
12. Would you ever expect the ball to spontaneously go from point B to point A? Why / Why not? /
Examine the diagram on the right.
There are two parallel metal plates.
Plate A is covered with negatively charged particles.
Plate B is covered with positively charged particles.
Charge “q” ( a negative - charge) is in between the plates and is free to move. /
13. Explain what will happen to charge q when it is released.
14. What happens to the velocity of charge q as it approaches plate B? Why?
15. Would you ever expect charge q to spontaneously go from point B to A? Why/ Why not?
Elaborate
Examine the drawing on the right.There are two metal plates set up like before.
This time there is a barrier preventing charges from directly passing from one plate to the other, but there is a wire connecting the plates.
16. What do you think will happen this time? /
This arrangement describes the basic components of a simple electric circuit.
When a large number of negative charges (or positive charges) are grouped together, there is a large amount of potential energy in the system.
If a path is set up that will allow those charges to move to places where they are less concentrated, then they will spontaneously move along that path.
That movement of charge along the path is called electric current.
When the negative charges move from a state of high concentration to low concentration, the potential energy in the system decreases.
17. If large numbers of charges squeezed together have high potential energy, what does that potential energy become as the charges move?
18. Give an example of another system that behaves the same way as this kind of electric circuit does.
19. Where do you think the electric potential energy in this circuit going? /20. What do you think is happening inside the wire that carries electric current?
Draw a picture and describe your ideas.
/ wireLet’s examine charges moving in the wire.
When there is no difference in the concentration of charged particles in a circuit, the electrons randomly move from one metal nucleus to another.
If a difference in concentration of charge occurs between the ends of the wire, there is a net flow or drift of the electrons from the end with a higher concentration of charge toward the end with the lower concentration of charge.
This movement decreases potential energy in the system.
Let’s examine this flow of charge with a model.
The diagram below represents a wire segment.
The white circles represent the positively charged nuclei of metal atoms in the wire.
Place a penny over nuclei 1, 2, 3, 4, 5 and 6.
21. What do you think the pennies represent?
Now we will apply a voltage to the system.
Draw a big (+) on the right hand side of the illustration, and a big (-) on the left hand side of the illustration.
The penny covering nucleus 6 is now in a high potential energy state and is attracted to the big (+) charge.
Pick it up and place it on the large positive charge you drew on the right hand side of the wire.
22. What does the ‘electron’ penny covering nucleus 5 now ‘see’?
23. What do you think the electron on nucleus 5 would do?
Move the electrons covering nucleus 5 in the manner you think appropriate.
Repeat this process with the electron covering nucleus 4.
24. What is the net direction that the electrons are moving?
We call this movement of electrons electron current.
25. What do you notice about the direction the ‘holes’ move?
(A ‘hole’ is the empty nucleus space remaining behind as an electron leaves it for an adjacent nucleus)
26. So we have a net flow of negative charge to the right and a net flow of ‘holes’ or positive charge states to the ...
We call this net movement of positive charge states to the left conventional current.
27. Look at the picture on the right. The top of the battery has a high concentration of + charge. Draw the direction of electron current, and the direction of conventional current in the wire. /28. Why do charges (electrons) move in an electric circuit?
29. What is electron current?
30. What is conventional current?
Evaluate
31. The number of electrons that pass a certain point in a conductor in a given amount of time is defined as
A) resistance B) charge C) potential difference D) electric current
32. An electric current in a metallic solid consists of moving
A) neutrons B) electrons C) protons D) nuclei
33. You are provided a battery, wire and a light bulb. Select the arrangement(s) that will cause the light bulb to glow.
AnswerBriefly explain your reasoning for your selection(s)
34. Select the illustration that represents a closed circuit.
AB
Briefly explain your reasoning for your selection(s)
35. Draw the path electricity follows through the light bulb shown in the illustration below.
36. Select the diagram that most accurately represents the path electricity follows in a light bulb holder.
A B C
Briefly explain your reasoning for your selection(s)
1