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**Electric and Magnetic Phenomena**

5. Electric and magnetic phenomena are related and have many practical applications. As a basis for understanding this concept: Standard 5 Electricity

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**1. Static electricity is a part of life**

1. Static electricity is a part of life. Can you name at least five examples of static electricity that occur in your home? 2. Fabric softeners are commonly used today because they eliminate static cling. Explain why clothes in the dryer get static cling. Electricity

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**3. Why can walking across a carpeted room be a shocking experience?**

4. Magnets have both north and south poles. While like poles repel each other, opposite poles attract each other. Explain the parallelism between magnetism and electric charge. Electricity

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**Electric Charge and Force**

Electricity Electric Charge and Force Electricity Electricity

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**Electric Charge Electrical property of matter**

Creates a force between objects Positive or Negative Electricity

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**Electric Charge Opposite charges Attract Like charges Repel**

Electricity

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3. The electric force between charged objects is c. either attractive or repulsive. Electricity

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**Electrical Charge Depends on the imbalance of electrons and protons**

Protons = positive Electrons = negative Neutron = neutral Leads to a net charge Electricity

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**2. When there is an equal amount of positive and negative charges on an object, the object is**

c. neutral. Electricity

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**Coulomb SI unit for charge Proton = +1.6 x 10-19 C**

Electron = -1.6 x 10-19C Charges are equal and opposite Electricity

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**Flow of Charge Conductor Insulator**

Material that transfers charge easily Insulator Material that does not transfers charge easily Electricity

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**Charging by Contact Electrons move from the rod to the doorknob**

Skill Builder: Interpreting Visuals, ATE p Have students explain what would happen if a positively charged rod were touched to the doorknob. Teaching Transparency TT 38 Charging by Contract is available as a visual aid. Electrons move from the rod to the doorknob Electricity Electricity

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**Charging by Contact Transfer of electrons**

Gives the doorknob a negative charge Electricity

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**Induced Charges Induces a positive charge near the rod**

Induces a negative charge away from the rod Skill Builder: Interpreting Visuals, ATE p Have students explain what will happen to the doorknob when the negatively charged rod is removed. Teaching Transparency TT 39 Induced Charges is available as a visual aid. Electricity Electricity

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**Induced Charges Electricity**

Discuss the polarization of the molecules in the tissue paper. Electricity Electricity

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i. Students know plasmas, the fourth state of matter, contain ions or free electrons or both and conduct electricity. Electricity

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Charging by Friction When rubbed together electrons can be transferred from one material to the other material that gets the electrons becomes negatively charged material that loses the electrons becomes positively charged Electricity

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**Electric Force The force of attraction or repulsion between objects**

Due to charge Without electric force life would be impossible Depends on charge and distance Attraction and repulsion are examples of Electric Force. Electricity Electricity

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**Electric Force Proportional to the product of the charges**

Inversely proportional to the distance between them squared Equation: F = q1 q2 /[4peo r2 ] Electricity

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e. Students know charged particles are sources of electric fields and are subject to the forces of the electric fields from other charges. Electricity

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**Electric Field Produced around charged particles**

Other charged objects around will experience an electric force Electric force acts through electric fields Electricity

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**4. Every charged particle produces d. an electric field.**

Electricity

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Point Charges Electric field lines point in the direction of the electric force on a positive charge Electricity

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**Point Charges Positive is attracted to negative**

Electric Field lines point inward Electricity

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**Electric Field Lines Show direction of electric force**

Also show relative strength Electricity

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Electric Fields Electricity

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Electric Fields In the figure shown, why do only half of the lines originating from the positive charge terminate on the negative charge? When compared to a 2 charge, there are c. twice as many field lines pointing outward from a 4 charge. Because the positive charge is twice as great as the negative charge. Electricity Electricity

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**Electric Force varies depending on**

charge and distance between charged objects Electricity

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Students know how to predict the voltage or current in simple direct current (DC) electric circuits constructed from batteries, wires, resistors, and capacitors. Electricity

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**b. Students know how to solve problems involving Ohm’s law.**

Electricity

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c. Students know any resistive element in a DC circuit dissipates energy, which heats the resistor. Students can calculate the power (rate of energy dissipation) in any resistive circuit element by using the formula Power = IR (potential difference) x I (current) = I 2 R. Electricity

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d. Students know the properties of transistors and the role of transistors in electric circuits. Electricity

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**Electrical Potential Energy**

Potential energy of charged object Due to its position in electric field Electricity

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**16. What determines the electrical potential energy of a charge**

Determined by the position of the charge relative to all the other electrical charges Electricity

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**Electrical Potential Energy**

Shows how the epe depends on the distance between the two charged particles. Electricity Electricity

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Electricity

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Potential Difference Change in the electrical potential energy per unit charge Measured in Joule / Coulomb 1 J/C = 1 volt or 1V or voltage Electricity

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**Volts Measure of potential difference**

Terminals of a battery have a potential difference Cell (battery) Source of current Voltage across the terminals Electricity

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**Dry Cell and Car Battery**

Electricity

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**Batteries Typically have one positive and one negative terminal.**

Electricity

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**Current Voltage sets charges in motion**

Current = Rate of electric charges moving through a conductor 1 C/s = 1 ampere or 1 amp Electricity

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Electric Current Produced when charges are accelerated by an electric field Charges move to a position of potential energy that is lower Electricity

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7. Current is the rate at which charges move through a(n) a. conductor. b. insulator. Electricity

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**Electrical Resistance**

What is the voltage from the wall? 120 V What is the power of a bulb? 40W, 60W, 100W Electricity

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**5. Resistance is caused by internal friction. 6**

5. Resistance is caused by internal friction. 6. The SI unit of resistance is the c. ohm. Electricity

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**Electrical Resistance**

Causes changes in current Caused by internal friction Slows the movement of charges through collisions Collisions can cause material to heat up Electricity

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**Electrical Resistance (Ohm’s Law)**

Resistance = voltage/current R = V / I = V / A = Ohm Electricity

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Resistance A set of electric trains is powered by a 9 V battery. What is the resistance of the trains if they draw 3.0 A of current? Answer: 3 Electricity

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Resistance A battery-operated CD player uses 12 V from the wall socket and draws a current of 2.5 A. Calculate the resistance of the CD player. Electricity

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Resistance There is a potential difference of 12 V across a resistor with 0.25 A of current in it. The resistance of the resistor is Answer: 48 Electricity

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Ohms Law A light bulb has a resistance of 12 . It is attached to a battery that has a voltage of 24 V. Calculate the current in the light bulb. Answer: 2 A Electricity

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Current A resistor has a resistance of 280. How much current is in the resistor if there is a potential difference of 120 V across the resistor? Answer: 0.43 A Electricity

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17. A resistor has a resistance of 1.8-ohm. How much current is in the resistor if there is a potential difference of 3.0 V across the resistor? Answer: 1.67 A Electricity

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9. A 13-ohm resistor has A of current in it. What is the potential difference across the resistor? Answer: V Electricity

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Electricity

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Series Circuits Electricity

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Series Circuits Electricity

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Parallel Circuits Electricity

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Parallel Circuits Electricity

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**18. Which bulb(s) will have a current in the schematic diagram above?**

Only the first light bulb will light. The other two bulbs are beyond the open switch and therefore, will not receive current. Electricity

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19. Does the schematic diagram above represent a series or parallel circuit? Answer: series circuit Electricity

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19. Does the schematic diagram above represent a series or parallel circuit? Electricity

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18. Is a current flowing in the schematic diagram above? Explain your answer. Electricity

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**Answer: Resistance drops to zero.**

10. What happens to the resistance of a superconductor when its temperature drops below the critical temperature? Answer: Resistance drops to zero. Electricity

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**Electric Energy Energy associated with electrical charges**

Whether moving or at rest Electricity

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**Electrical Power Rate at which electrical energy is used in a circuit**

power = current x voltage P = IV 1 Watt = 1 Amp x 1 Volt Electricity

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**A color television draws about 2**

A color television draws about 2.5 A when it is connected to a 120 V outlet. Assuming electrical energy costs $0.060 per kWh, what is the cost of running the television for exactly 8 hours? Answer: $0.14 Electricity

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8. A flashlight bulb with a potential difference of 4.5 V across its filament has a power output of 8.0 W. How much current is in the bulb filament? Answer: 1.8 A Electricity

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Household Circuits Electricity

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7. What is the potential difference across a resistor that dissipates 5.00 W of power and has a current of 5.0 A? Answer: 1.00 V Electricity

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11. If a lamp is measured to have a resistance of 120- when it operates at a power of 120 W, what is the potential difference across the lamp? Answer: 120 V Electricity

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12. A microwave draws 5.0 A when it is connected to a 120 V outlet. If electrical energy cost $0.090/kWh, what is the cost of running the microwave for exactly 6 hours? Answer: $0.32 Electricity

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13. What happens to the overall resistance of a circuit when too many appliances are connected across a 120 V outlet? Answer: Resistance is decreased. Electricity

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11. An electric toaster has a power rating of 1100 W at 110 V. What is the resistance of the heating coil? Answer: 11 Electricity

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13. A device that protects a circuit from current overload is called a(n) Answer: circuit breaker. Electricity

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14. What is charging by contact? Electricity

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16. A 180-ohm resistor has 0.10 A of current in it. What is the potential difference across the resistor? Answer: 18 V Electricity

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**Study Guide Attraction, repulsion Electric force Batteries**

Current, potential Resistance Ohm’s law: V=IR Power, P = VI Circuits, parallel, series Charge/ing, Electric fields Conductor, insulator Electricity

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