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Revision Sheet for the Final Exam

Academic Year: 2018/2019 – First Term Subject: Physics Grade: 12 Student’s name:………………………. Date: 26/11/2017 Required Material: Chapter 16: Electric Forces and Fields, Sections: (1, 2, & 3) textbook pages: (547-577) Chapter 17: Electrical energy and current, Sections: (3 & 4) textbook pages: (594-609)

Exam date: Tuesday 4/12/2018

Chapter.16 / Section.1: Electric Charge

Q.1: Write the letter of the correct answer in the space provided.

_____ 1. What happens when a rubber rod is rubbed with a piece of fur, giving it a negative

charge?

a. Protons are removed from the rod.

b. Electrons are added to the rod.

c. Electrons are added to the fur.

d. The fur is left neutral.

_____ 2. Electric charge is

a. found only in a conductor. c. found only in insulators.

b. conserved. d. not conserved.

_____ 3. Charge is most easily transferred in

a. nonconductors. c. semiconductors.

b. conductors. d. insulators.

_____ 4. Conductors can be charged by _______________, while insulators cannot.

a. grounding c. polarization

b. induction d. contact

Q=Ne Total Charge=number of electrons transferred × fundamental charge

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______ 5. If a positively charged glass rod is used to charge a metal bar by induction, the charge

on the bar

a. will be equal in magnitude to the charge on the glass rod.

b. must be negative.

c. must be positive.

d. will be greater in magnitude than the charge on the glass rod.

______ 6. Which sentence best describes electrical conductors?

a. Electrical conductors have low mass density.

b. Electrical conductors have high tensile strength.

c. Electrical conductors have electric charges that move freely.

d. Electrical conductors are poor heat conductors.

Q.2: A negatively charged rubber rod has a 8.7 µC of charge. How many excess electrons are

on the rod?

Q.3: A balloon is negatively charged by rubbing and then clings to a wall. Does this mean

that the wall is positively charged?

………………………………………………………………………………………………………………………………………………….. ………………………………………………………………………………………………………………………………………………….. …………………………………………………………………………………………………………………………………………………..

Q.4: Compare charging by contact and charging by induction.

charging by contact charging by induction

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Chapter.16 / Section.2: Electric Force

Coulomb constant: kC 8.99 109 N•m2/C

2

Q.1: An electron is separated from a potassium nucleus (charge 19e) by a distance

of 5.2 1010 m. What is the electric force between these particles?

Q.2: Two electrostatic point charges of 20.0 µC and 30.0 µC exert attractive forces on

each other of 145 N. What is the distance between the two charges?

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Q.3: Two small positively charged spheres have a combined charge of 5 109

C. If each

sphere is repelled from the other by an electrostatic force of 1.0 N when the spheres are 2.0m

Apart, what is the charge on each sphere?

Q.4: Consider three point charges on the x-axis: q1 4.92 109

C is at the origin,

q2 6.99 108

C is at 3.60 101

m, and q3 5.65 109

C is at

1.44 m. Find the magnitude and direction of the resultant force on q1.

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Q.5: A charge of 4.5 nC and a charge of 2.0 nC are seperated by 50 cm. Find the equilibrium

psition for a -3.8 nC charge.

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Chapter.16 / Section.3:The Electric Field

Q.1: An electric field of 2.6MN/C is directed along the positive y-axis. What is the electric

force on a 6.0 nC charge in this field?

Q.2: An electric field of 3.0 103 N/C is directed downward. If the electric force on a charge

is 2.86 106

N, what is the charge?

Q.3: What is the electric field strength at a distance of 29 cm from a charge of 6µC?

E = Felectric / qo

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Q.4: What size of charge is necessary to create an electric field strength of 8.3 x 105 N / C at

a distance of 6 cm?

Q.5: A charge, q1 15.0 C, is at the origin, and a second charge, q2 5.00 mC, is on the y-

axis 0.500 m from the origin. Find the magnitude and direction of the electric field at a

point on the y-axis 1.00 m from the origin.

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Q.6: Two equal charges of 3.00 C lie along the x-axis: one is at the origin, and the other is

- 1.0 m from the origin. Find the magnitude and direction of the electric field at a point on

the y-axis 0.30 m from the origin.

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Chapter.17 / Section.3: Current and Resistance

Q.1: Write the letter of the correct answer in the space provided.

_____ 1. Electric current in a wire is the

a. number of electric charges moving from one location to another in the wire.

b. net movement of electrical energy through the wire.

c. rate at which electric charges move through an area of the wire.

d. rate at which electrical energy is used to move charges through the wire.

_____ 2. One ampere of current is the movement of ______________ through a given area

in one second.

a. one coulomb of charge

b. one volt of potential difference

c. one joule of energy

d. one electron

_____ 3. The diagram to the right represents a wire in which the

net flow of electrons is to the right. The direction of

the conventional current in the wire

a. depends on the potential difference.

b. is to the left.

c. is the same direction as the electron flow.

d. cannot be determined.

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_____ 4. The speed at which an electron moves in an electric field in a conductor is the

a. speed of light.

b. average collision speed.

c. drift velocity.

d. average electron speed.

_____ 5. When a current moves through a copper conductor, electrons collide with copper

atoms. The result of these collisions is

a. an increase in voltage.

b. a decrease in resistance.

c. an increase in temperature.

d. a decrease in voltage.

_____ 6. The current of a non-ohmic material is plotted against the applied potential. How

would you describe the resulting graph?

a. The graph will have a constant positive slope.

b. The graph will have a variable positive slope.

c. The graph will have a variable negative slope.

d. The graph will have a constant negative slope.

_____ 7. Which factor is least likely to affect the resistance of a conductor?

a. the length of the conductor

b. the temperature of the conductor

c. the overall shape of the conductor

d. the material the conductor is made from

Q.2: A total charge of 114 C passes through a cross-sectional area of an aluminum wire

in 0.36 s. What is the current in the wire?

Q.3: A total charge of 29 mC passes through a cross-sectional area of a nichrome wire

in 11 s. What is the current in the wire?

Q.4: If a current in a wire of a telephone is 1.4 A, how long would it take for 98 C of charge

to pass a point in this wire?

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Q.5: If a current in a wire of a vacuum cleaner is 9.65 A, how long would it take for 30.9 C

of charge to pass a point in this wire?

Q.6: A photocopy machine draws 9.3 A when it starts up. If the start-up time is

15 s, how much charge passes a cross-sectional area of the circuit in this time?

Q.7: A computer draws 3.0 A when it starts up. If the start-up time is 2.0 min, how much

charge passes a cross-sectional area of the circuit in this time?

Q.8: A television set is plugged into a 120 V outlet. The television circuit carries a current

equal to 0.75 A. What is the overall resistance of the television set?

Q.9: A medium-sized household oscillating fan draws 545 mA of current when the potential

difference across its motor is 120 V. How large is the fan’s resistance?

Q.10: A washing machine motor carries a current through a circuit with a resistance of 12.2

. If the washing machine is plugged into a 120 V outlet, what is the current in the

motor?

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Q.11: Calculate the current that a laptop computer would draw from a 120 V outlet in the

United States if the computer has a resistance of 40.0 . Then, calculate the current that the

same computer would draw if you plugged it into a 240 V outlet in the United Arab

Emirates.

Q.12: What is the potential difference across a 5.0 resistor that carries a current of 5.0 A?

Q.13: A prototype electric car is powered by a 312 V battery pack. What is the resistance of

the motor circuit when 2.8 105 C passes through the circuit in 1.00 h?

Q.14: Is current ever “used up”? Explain your answer.

………………………………………………………………………………………………….

………………………………………………………………………………………………….

Q.15: Why do wires usually warm up when an electric current is in them?

………………………………………………………………………………………………….

………………………………………………………………………………………………….

Q.16: What is the relationship between resistance and temperature? Explain.

………………………………………………………………………………………………….

………………………………………………………………………………………………….

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Chapter.17 / Section.4: Electric Power

Q.1: Write the letter of the correct answer in the space provided.

_____ 1. In alternating current, the charge carriers move

a. in all directions.

b. in only one direction.

c. repeatedly in one direction then in the opposite direction.

d. from a lower to a higher electric potential.

_____ 2. Electrical appliances have labels that state the power used by the appliance. What

does the power rating listed on the label represent?

a. the amount of current the appliance uses

b. the amount of electrical energy converted to heat or light by the appliance

c. how quickly the appliance heats up

d. the amount of energy converted each second into other forms of energy

_____ 3. Electric power is the rate at which charge carriers

a. pass through an area.

b. do work.

c. move through a potential difference.

d. collide with atoms.

_____ 4. Which statement is correct regarding electric power?

a. Electric power equals current times resistance.

b. Electric power equals the amount of electrical energy used by a device.

c. Electric power equals the current times potential difference.

d. Electric power equals the amount of electrical energy converted to other forms

of energy.

P = I2R electric power = (current)2×resistance

P = ∆𝑽

𝑹

electric power = (potential difference)2/resistance

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Q.2: If an alarm clock is plugged into a 120 V outlet, the electric current in the clock’s circuit

is 4.2 102 A. How much power does the alarm clock use?

Q.3: A generator at a central electric power plant produces electricity with a potential

difference of 2.5 104 V across power lines which carry a current of 20.0 A. How much

power does the generator produce?

Q.4: If the potential difference across an electric sport car motor’s is 720 V and the resistance

was 0.30 , how much power was needed for the car to run?

Q.5: A light bulb has a filament with a resistance of 144 , while a second bulb has a

filament with a resistance of 240 . Both bulbs are connected across a 120 V outlet.

Which light bulb is brighter? [Hint: The brightest bulb uses the most power.]

Q.6: A group of students built a car that combines a conventional diesel engine and an

electric direct-current motor. The power delivered by the motor is 32 kW. If the

resistance of the car’s circuitry is 8.0 , find the current drawn by the motor.

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Q.7: Fuel cells combine gaseous hydrogen and oxygen to effectively and cleanly produce

energy. Recently, German engineers produced a fuel cell that can generate 4.2 1010 J of

electricity in 1.1 103 h. What potential difference would this fuel cell place across a

40.0 resistor?

Q.8: An electric kettle requires 370 W of power to boil water. If the kettle is plugged into a

120 V outlet, what is the resistance in the kettle’s circuit?

Q.9: A fuel cell has been developed that can generate 1.06 104 W of power. If this fuel cell

has a current of 16.3 A, what is the potential difference across the fuel cell?

Q.10: The first American hybrid electric bus operated in New York in 1905. The gasoline-

fueled generator delivered 33.6 kW to power the bus. If the generator supplied an emf of

4.40 102 V, how large was the current?

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Q.11: A toaster is connected across a 123 V outlet and dissipates 0.95 kW in the form of

electromagnetic radiation and heat. What is the resistance of the toaster?

Q.12: If a 325 W heater has a current of 6.0 A, what is the resistance of the heating element?

Please revise all the works that we have done in the copybook, worksheets,

assessments, and homework.

It will be useful if you can log into the online textbook and resources using your

username and password.

Good luck in your exam