22 electric current - humble independent school district · mainidea explain how charged particles...

22 Electric CurrentBIGIDEAWrite the Big Idea for this chapter.

Use the “What I Know” column to list the things you know about the Big Idea. Then list the questions you have about the Big Idea in the “What I Want to Find Out” column. As you read the chapter, fill in the “What I Learned” column.

KWhat I Know

WWhat I Want to Find Out

LWhat I Learned

Science Notebook • Electric Current327

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22 Electric Current 1 Current and Circuits

MAIN IDEAWrite the Main Idea for this lesson.

Recall and write the definition of the Review Vocabulary term.

electric potential difference

Use your book to define each term.

electric current

conventional current

battery

electric circuit

ampere

resistance

resistor

parallel connection

series connection

REVIEW VOCABULARY

electric potential

difference

NEW VOCABULARY

electric current

conventional current

battery

electric circuit

ampere

resistance

resistor

parallel connection

series connection

5(F)





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-Hill Education. Perm

ission is granted to reproduce for classroom use.

1 Current and Circuits (continued)

Explain how you can maintain a potential difference between two plates connected by a conductor.

Draw a flow chart showing how a water wheel transforms potential energy into work done by a motor.

GET IT? Draw a diagram of an electric circuit, and explain how energy is conserved in it.

GET IT? Restate the equations for power using the variables: energy (E), charge (q), and current (I).

Student Edition, pp. 598–600





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TRY IT!

Problem

ELECTRIC POWER AND ENERGY A 12.0-V battery delivers a 0.75-A current to an electric motor connected across its terminals.

a. What power is delivered to the motor?

b. If the motor runs for 5.0 min, how much electrical energy is delivered?

1. ANALYZE AND SKETCH THE PROBLEM

KNOWNS UNKNOWNS

ΔV =

I =

t =

= ?

= ?

2. SOLVE FOR THE UNKNOWN

a. Use P = IΔV to find power.

b. Use the relationship between energy and power.

3. EVALUATE THE ANSWER

• Are the units correct?

• Is the magnitude realistic?

Student Edition, p. 601

Use with Example Problem 1.

Use this column for

scratch work and

sketches.





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GET IT? Explain how a schematic of an electric circuit compares to an artist’s drawing of the same circuit.

GET IT? Identify what an ammeter and a voltmeter measure.

Draw symbols for the following elements commonly found in electric circuit diagrams.

Ammeter Ground

Battery Lamp

Capacitor Resistor

Fuse Voltmeter







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GET IT? Define resistance in your own words.

Describe how resistance changes when each of the physical factors in the table increases.

Length

Cross-sectional area

Temperature

GET IT? Explain which devices obey Ohm’s law.

GET IT? List two ways to control the current flowing through a simple circuit.

Evaluate If a variable resistor decreases the amount of wire in a circuit that contains a motor, what happens to the speed of the motor?





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Use with Example Problem 2.

Use this column for

scratch work and

sketches.

TRY IT!

Problem

CURRENT THROUGH A RESISTOR A 12.0 V battery is connected to a 15.0-Ω resistor. What is the current in the circuit?

1. ANALYZE AND SKETCH THE PROBLEM

KNOWNS UNKNOWN

ΔV =

R =

= ?

2. SOLVE FOR THE UNKNOWN

Use I = ΔV _ R

to determine the circuit.

3. EVALUATE THE ANSWER

• Are the units correct?

• Is the magnitude realistic?

Draw a parallel and a series circuit in the boxes below.

Parallel circuit Series circuit





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Fill in the blanks in the sentence about different types of electrical connections.

The terms voltage across are associated with a

connection, while the terms current through are associated with a

connection.


Student Edition, p. 608

SUMMARIZE

How does the MAINIDEA for this section relate to the chapter’s BIGIDEA?

REVIEW IT!

19. MAINIDEA Explain how charged particles are related to electric current, electric circuits, and resistance.

20. Schematic Draw a schematic diagram of a circuit that contains a battery and a lightbulb. Make sure the lightbulb will light in this circuit.





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21. Resistance Joe states that because R = ΔV _ I , if he increases the voltage, the resistance

will increase. Is Joe correct? Explain.

22. Power A circuit has 12 Ω of resistance and is connected to a 12-V battery. Determine the change in power if the resistance decreases to 9.0 Ω.

23. Resistance You want to measure the resistance of a long piece of wire. Show how you would construct a circuit with a battery, a voltmeter, an ammeter, and the wire to be tested to make the measurement. Specify what you would measure and how you would compute the resistance.

24. Energy A circuit transforms 2.2×103 J of energy when it is operated for 3.0 min. Determine the amount of energy it will transform when it is operated for 1 h.

25. Critical Thinking We sometimes say that power is “dissipated” in a resistor. To dissipate is to spread out or disperse. In what sense is something being dispersed when charge flows through a resistor?






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22 electric current - humble independent school district · mainidea explain how charged particles...

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