CASTLE KIT Section 1 Study Guide
Summary
INVESTIGATION ONE: WHAT IS NEEDED TO LIGHT A BULB?
Explores the need for a closed loop to make the bulbs light. When there is a gap anywhere in the loop, the bulbs go out.
INVESTIGATION TWO: IS THERE ANYTHING HAPPENING IN THE WIRES?
A compass is used to detect activity in the wires. When the battery is reversed, the compass needle deflects in the opposite direction.
INVESTIGATION THREE: TESTING CONDUCTORS AND INSULATORS
Using a simple test circuit, conductors and insulators are identified. The bulb socket is tested for conductivity. A household bulb and a flashlight bulb are also tested for conductivity. To light a single bulb with one cell and one wire, the complete path must include both ends of the cell and both the bulb’s tip and threaded section.
After completing Section 1, you should be able to:
• Explain why bulbs will not light if there is a break in a continuous closed loop.
• Identify loops in which bulbs will and will not light by inspecting diagrams.
• Based on compass observations, explain why there is a one-way direction of flow in a closed loop.
• Draw a circuit as an unbroken loop of electrical components that forms a continuous conducting path.
• Using words and arrows, describe the direction of conventional charge flow in a circuit.
• Describe the differences observed when testing conductors and insulators.
• Explain how conductors and insulators relate to a “continuous conducting path”.
• Draw the conducting path through a light bulb.
• Draw the conducting path through a circuit using “conventional” charge flow direction.
Review Questions:
1-3, use the picture to the right
1. Are there any breaks of insulators in this circuit? If so, mark them on the sketch.
2. Is this circuit a continuous conducting path? Cite evidence to support your answer.
3. On the diagram, draw a colored line to indicate the path along which you think the moving charge travels. Draw arrows to indicate the direction the charge travels, based on the established convention.
4. What evidence could you provide to suggest that something happens in the wires when the bulbs are lit?
5. What is your present working hypothesis about what is happening in the wires when the bulbs are lit?
6. What happens in the wires when the battery connections are reversed? What is your evidence?
7. What is the battery doing when the bulbs are lit?
8. Based on the assumption that something flows through wires when bulbs are lit in a circuit, is the direction of the flow the same in all the wires, or does it vary in different parts of the circuit? What is the evidence for your answer?
9. What materials and conditions must be present for a bulb to light? Explain carefully.
10. On this cross-section diagram of a bulb in its socket, draw a heavy line to show a continuous conducting path that starts at a wire attached to one clip, goes through the bulb and exits through a wire at the other clip.
11. Based on your observations and ideas up to this point, how would you define the term ‘electricity’.
12. In the following circuit, which bulb lights first? ______
(A) Bulb A
(B) Bulb B
(C) Bulb C
(D) They all light at the same time.
(E) Bulbs A and C light first, then bulb B lights
Explain your answer.
13. Study the three loops shown below. For each loop, state which of the bulbs will light.
14. Study the two circuits below in which a paper clip has been inserted between wires in a circuit.
Which of the following statements are true? ______
(A) The bulb will light more brightly in Circuit A .
(B) The bulb will light more brightly in Circuit B
(C) The bulb will be the same brightness in either case.
(D) The bulb will not light.
15. Support your answer to Question #14 using the words “insulator” and “conductor” correctly as part of your explanation.
16. Write in your own words a definition of the word circuit which anyone could use to determine if a given set of connections is or is not a circuit.
17. We have observed in several activities that as soon as a very small gap is produced anywhere in the circuit, the bulbs go out. Would you classify air as a conductor or an insulator? Explain.
18. Indicate whether each of the following statements is True or False. Then state evidence which either supports or contradicts each statement.
___ (A) Charge moves out of both ends of the battery into the loop.
Evidence:
___ (B) Light bulbs are non-directional devices. (Whichever way they are connected in the circuit, they behave the same way if you turn them around.)
Evidence:
___ (C) The battery determines the direction of flow of charge in a circuit.
Evidence:
___ (D) A compass can be used to determine the exact direction that charge flows in a circuit.
Evidence:
___ (E) Metal substances are generally conductors.
Evidence:
19. A group of adventurous students decided to see if it is possible to light two bulbs at once without any sockets using a 3-cell battery. Figure 1 shows a set of connections they discovered in which both bulbs lit.
(A) Draw a colored line which shows the continuous conducting path.
(B) Figures 2 and 3 show some other possible connections. Decide which, if any, bulbs will light and draw a line showing the continuous conducting path.
Current Electricity Review
Vocabulary: Circuit, closed loop, series circuit, parallel circuit, resistor, capacitor, switch, battery, current, amperage, resistance, open loop
Current Electricity: “Moving Electricity,” electrons ______through a wire and can do ______.
Current letter abbreviation: Current unit:
Voltage letter abbreviation: Voltage unit:
Resistance letter abbreviation: Resistance unit:
Circuit Symbols: (Draw a symbol for the circuit parts below)
Wire Battery Light bulb Switch Resistor
Fill in the blank: (Complete the sentences below)
· A resistor is an electrical device that makes it harder for the ______to flow.
· Voltmeter: measures the ______(voltage) between 2 points in a circuit.
· Ammeter: measures ______.
· Ohm’s Law: current is ______to voltage, and ______to resistance.
Example Ohm’s Law Problems (Draw a circuit diagram for each):
1. When a 12 volt battery is connected to a light bulb, 6 amps of current are measured. Find the resistance of the bulb.
2. The motor connected in a circuit draws 3 amps of current when it is running. Find the voltage of the battery if there is a 30 Ohm resistance.
3. When a heater, which provides 12 Ohms of resistance is plugged into a wall socket (120 V) what will the current flowing through the heater be?