Name: ____________________________ Homeroom: _____________

GRADE 9 SCIENCECHAPTER 8:

OMH’S LAW DESCRIBES THE RELATIONSHIP OF CURRENT, VOLTAGE, AND RESISTANCE

Section Outline and Study Guide:

1. Electrochemical Cellsa. What is potential energy?b. Explain how an electrochemical cell works.

2. Current Electricitya. Define current electricity.b. Define and identify the unit used to measure: electric potential difference (voltage), electrical current, and electrical resistance.

3. Electric Circuitsa. Describe the 4 parts of an electric circuit (source, load, switch, and conductor).b. Create circuit diagrams using symbols for: bulb, cell, battery, wire, resistor, ammeter, voltmeter, open switch, closed switch.c. List 4 factors that affect the amount of resistance in a wire (length, diameter, type, temperature).

4. Ohm’s Lawa. State Ohm’s Law. b. Given any 2 values for voltage, current and resistance, use Ohm’s Law to calculate the missing value.c. Use an ammeter and voltmeter to measure current and voltage in a circuit.

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Key TermsAmperes Electric load Ohm’s Law

Battery Electrical resistance Potential difference

Circuit diagrams Electrochemical cells Resistance

Current Electricity Electrodes Resistor

Electric potential energy Electrolyte Volt

Electric circuit Energy Voltage

Electric current Ohm

Use the word bank above to complete the following definitions.1._______________________: A combination of electrochemical cells connected together.2._____________________: Converts chemical energy into electrical energy. Consists of two different electrodes and an electrolyte.

3._____________________: Electric energy that is stored in a battery.

4._____________________: Another term for voltage.

5._____________________: The change in electric potential energy per coulomb of charge.

6._____________________: The unit used to measure potential difference.7._____________________: The two terminals in a cell; made of two different metals/ materials.

8._____________________: A gel or paste that conducts electric current in a cell.9.____________________: The continuous flow of charge in a complete circuit.

10.______________________: A complete pathway that allows electrons to flow.11.____________________: A drawing using symbols to represent different components of a circuit.12._____________________: Any device that transforms electrical energy into other forms of energy; examples include light bulbs, buzzers, and motors.13._____________________: The unit for measuring electric current.14._______________________: The amount of charge passing a point in a conductor every second.

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15._______________________: The property of any material that slows down the flow of electrons.

16.______________________: The ratio of voltage to current. Can be calculated using Ohm’s Law.

17.______________________: The unit for measuring electrical resistance.

18.______________________: The mathematical relationship comparing voltage, current and resistance.

19.______________________: An electrical component with a set amount of resistance that slows down current and converts electrical energy into other forms of energy.

20.______________________: the ability to do work.

What is an Electrochemical Cell? Electrochemical cells convert ___________________ energy into

___________________ energy. There are two main components:

1. Electrodes Must be made of two _________________________ materials. Are the ______________________ and _____________________ terminals. Electrons flow from the ________________________ terminal to the

________________________ terminal.2. Electrolyte

A _____________________ or _____________________ that the electrodes are submersed in.

Allows ____________________ to flow between electrodes.

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How Does an Electrochemical Cell Work? A chemical reaction occurs between the _______________________ and one

of the _______________________, causing it to lose _______________________. The electrode that loses electrons acquires a _______________________

charge and is known as the _______________________ terminal. These electrons flow through the _______________________ and are

collected on the other electrode. The electrode that gains electrons acquires a _______________________

charge and is known as the _______________________ terminal. Once the cell is connected in a ____________________, electrons can flow. Electrons leave from the _______________________ terminal of a cell and re-

enter through the _______________________ terminal.

Draw arrows on the circuit below to show which way the electrons are travelling.

NOTE: A _________________________ is a combination of electrochemical cells

connected together.

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Electrical Potential Energy Electric Potential Energy is ____________________ electrical energy. An example is the energy stored in a ____________________. The electrons

have stored energy that can be used once the battery is connected in a circuit.

Potential Difference The change in potential energy per _______________________ of charge. Also called ________________________!

Electric Circuits A complete pathway that allows _____________________ to flow. Will transform ______________________ energy into other forms of energy.

What are the four Components of a Circuit?1. Source

Provides the ____________________ energy. Example: _____________________________________________________

2. Conductor Wire through which the ____________________ flow. Example: _____________________________________________________

3. Switch Turns the circuit __________ or __________. Example: _____________________________________________________

4. Load Transforms ______________________ energy into other forms of

energy. Example: _____________________________________________________

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Label the 4 components of the circuit!

Circuit Diagrams Use ____________________ to represent the different components of a

circuit.Fill in the names of the symbols listed below (see page 262).

Symbol Name Symbol Name

Using the appropriate symbols, draw a proper circuit diagram for the following:

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UNIT 3 Circuit Symbols BLM 3-19

Goal • Assess your knowledge of symbols related to circuitry.

What to Do Draw the circuit symbol for each component.

Component Circuit Symbol

1.conducting wire

2.bulb

3.voltmeter

4.open switch

5.cell

6.closed switch

7.battery (3 cells)

8.ammeter

9. resistor

Short Answer Question

10. Define each of the following terms.(a)Source _____________________________________________________________________ _____________________________________________________________________(b)Conductor _____________________________________________________________________

_____________________________________________________________________(c)Load

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__________________________________________________________________________________________________________________________________________(d)Switch _____________________________________________________________________

_____________________________________________________________________

UNIT 3 Drawing Circuit Diagrams BLM 3-18

Goal • Practise drawing circuit diagrams.

What to DoComplete the questions to show what you know about drawing circuit diagrams.

1. Circuit A (a) Draw a circuit diagram.

(b) Is this circuit open or closed? ____________

(c) If this is a closed circuit, what is the source of the potential difference? __________________

What is the load? __________________

2. Circuit B (a) Draw a circuit diagram.

(b) Is this circuit open or closed? ____________

(c) If this is a closed circuit, what is the source of the potential difference? __________________

What is the load? __________________

3. Circuit C (a) Draw a circuit diagram.

(b) Is this circuit open or closed? ____________

(c) If this is a closed circuit, what is the source of the potential difference? ___________________

What is the load? ___________________

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Electric Current The amount of ____________________ passing a given point in a conductor

per second. Measured in ____________________ (A). Measured using an ___________________.

Electric Resistance Slows down the flow of ______________ and transforms _______________

energy into other forms of energy. Measured in ___________________ (Ω).

Ohm’s Law The mathematical relationship comparing _____________ (V),

_______________ (I), and _______________ (R).

Fill in the triangle to describe the relationship between V, I and R.

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UNIT 3 Ohm’s Law BLM 3-24

Goal • Review your understanding of how to use Ohm’s law.

Questions1.What is the resistance of a toaster if a current of 12.5 A flows through it

when it is connected to 120 V?

2.A light bulb has a resistance of 90 . What current flows through the bulb when it is connected to 120 V?

3.A current of 0.50 A flows through a light bulb that has a resistance of 18 . What is the voltage across this light bulb?

4.A flashlight bulb has a resistance of 4.0 . What current passes through the bulb if it is connected to 3.0 V?

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5.What potential difference is necessary to produce a current of 0.60 A in a load that has a resistance of 25 ?

UNIT 3 Calculating Practising Resistance BLM 3-26

Goal • Practise calculating resistance.

What to DoRead pages 273 and 274 of Discovering Science 9. Use the practice problems to help you calculate answers to the following questions. Show all your work.

 1.Only 0.0025 A of current pass through a portable CD player. If the CD player is operated by a 9.0 V battery, what is the resistance within the circuit?

 2.An automobile headlight has an average resistance of 24 . Car batteries provide a potential difference of 12 V. What amount of current passes through the headlight?

 3. In a portable radio, 0.50 A of current are flowing through a conductor that provides 18 of resistance. What potential difference is provided by the battery?

 4.A clothes dryer uses a 220 V power source. The coils of the heater provide an average resistance of 12 . What amount of current is flowing through the heating coils?

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 5.A 9.0 V battery maintains a current of 3.0 A through a portable radio. What is the resistance of the conductor?

 6.What is the resistance of a hair dryer plugged into a 110 V outlet with a 10 A current flowing through it?

 7.A light bulb will allow 0.50 A to flow through it. If the outlet provides a potential difference of 110 V, how much resistance is provided by the bulb?

 8.An automobile headlight has a resistance of 40 when attached to a standard 12 V battery. How much current flows through the headlight?

 9.A portable CD player, operating with four 1.5 V batteries connected in series, provides a resistance of 15 000 . What amount of current is flowing through the CD player?

10. An electric motor has an operating resistance of 25 when a 4.8 A current is flowing through it. What is the potential difference of the outlet

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the motor is plugged into?

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What Factors Affect the Amount of Resistance in a Wire?

1. Length Longer the wire = _____________ resistance.

2. Diameter Greater diameter = _____________ resistance.

3. Temperature Warmer wire = _____________ resistance.

4. Type Different types of wires offer different amounts of resistance. For example, copper wire offers _______________ resistance than

tungsten wire.

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UNIT 3 Chapter 8 Review edited BLM 3-30

Goal • Check your understanding of Chapter 8.

What to DoCircle the letter of the best answer.

 1. Which combination of materials could be used to produce the best electrochemical cell?A.an aluminum electrode, a copper electrode, and an acidic solution B.an aluminum electrode, a copper electrode, and waterC.two silver electrodes and an acidic solutionD.two silver electrodes and water

 2. Which is not an electric load?A.batteryB.buzzer C. light bulbD.resistor

 3.Which statement correctly defines the difference between static electricity and current electricity?A. In static electricity, the charge stays in one place, whereas current

electricity is the flow of charge in a circuit. B.Static electricity is the flow of charge in a circuit, whereas in current

electricity the charge stays in one place.

C.Static electricity is the flow of negative charge, whereas current electricity is the flow of positive charge.

D.Static electricity is the flow of positive charge, whereas current electricity is the flow of negative charge.

 4. Which correctly defines current?A. the current caused by sources other than batteries B. the flow of charge from negative to positiveC.the flow of charge from positive to negativeD.the flow of electrons

 5.What is the name of an electric device that slows down current and changes electrical energy into other forms? A.batteryB.conductorC.resistorD.switch

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 6. What is the purpose of an ohmmeter?A. to measure chargeB. to measure currentC.to measure resistanceD.to measure voltage

 7. A current of 2.0 A flows through a 12 resistor. What is the voltage across this resistor?A.2.0 VB.6.0 VC.12 VD.24 V

Match the Term on the left with the best Descriptor on the right.Each Descriptor may be used only once.

Term Descriptor

_____ 8. voltmeter_____ 9. ammeter_____ 10. current_____ 11. voltage_____ 12. resistance_____ 13. circuit

A. the amount of charge passing a given point per second

B. a device used to measure current

C. a complete path for current to travel

D. a device used to measure potential difference

E. slows down the movement of charge

F. the flow of positive chargeG. the amount of electric potential

energy per unit of charge

Short Answer Questions14. Draw a circuit diagram for the following circuit.

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15. Calculate the following using Ohm’s law.(a) A light bulb is connected to a 9.0 V battery. The current through the

light bulb is measured to be 300 mA. What is the resistance of the light bulb?

(b) A 16 V source is connected to a 2500 load. What is the current through this load? Give your answer in both amperes (A) and milliamperes (mA).

16. You are given a load of an unknown resistance. Describe how you would determine this load’s resistance using a battery, voltmeter, ammeter, and connecting wires. _________________________________________________________________________________________________________________________________________________________________________________________________________

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