Science 30 U c: e e€¦ · assignmenT BookleT c1 science 30: UniT c chapTer 1 assignmenT This Assignment Booklet is worth 95 marks out of the total 152 marks for the assignments

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Science 30Unit c: electromagnetic energy

aSSignment Booklet c1


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Science 30Unit C: Electromagnetic EnergyAssignment Booklet C1Chapter 1 Assignment

For Teacher’s Use only

summary Teacher’s comments

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Chapter 1Assignment 95

Exploring the electronic information superhighway can be educational and entertaining. However, be aware that these computer networks are not censored. Students may unintentionally or purposely find articles on the Internet that may be offensive or inappropriate. As well, the sources of information are not always cited and the content may not be accurate. Therefore, students may wish to confirm facts with a second source.

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Copyright © 2007, Alberta Education. This resource is owned by the Crown in Right of Alberta, as represented by the Minister of Education, Alberta Education, 10155 – 102 Street, Edmonton, Alberta, Canada T5J 4L5. All rights reserved.

This resource was developed by or for Alberta Education. It may be reproduced in any form, including photocopying, without written permission from Alberta Education provided that associated copyright notices are also reproduced.

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1 Assignment Booklet C1Science 30: Unit C


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assignmenT BookleT c1science 30: UniT c

chapTer 1 assignmenT

This Assignment Booklet is worth 95 marks out of the total 152 marks for the assignments in Unit C. The value of each assignment and each question is stated in the left margin.

Read all parts of your assignment carefully, and record your answers in the appropriate places. If you have difficulty with an assignment, go back to the textbook and review the appropriate lesson. Be sure to proofread your answers carefully before submitting your Assignment Booklet.

chapter 1 assignment: electric and magnetic Fields

For questions 1 to 4, read each question carefully. Decide which of the choices BEST completes the statement or answers the question.

1. During a lightning strike, 24 C of charge moved from the bottom of a cloud to the top of a water tower. The charge moved across an electric potential difference of 1.2 ¥ 108 V. What amount of energy was released during the lightning strike?

A. 2.88 ¥ 109 J B. 2.00 ¥ 10- 7 J C. 1.17 ¥ 107 J D. 3.60 ¥ 108 J

2. A student drew field lines around a spherical source.

The student did not indicate what kind of field the diagram represented. The student’s diagram most likely represents

A. an electric field around a positively charged ball B. an electric field around a negatively charged ball C. a gravitational field around a massive ball D. a magnetic field around a magnetized ball

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Assignment Booklet C1Science 30: Unit C


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1 3. Which of the following can function as test bodies in a magnetic field?

A. grass seeds B. compass needles C. tiny ebony particles D. negatively charged strips of paper

4. Which of the following is a source of a magnetic field?

A. an ebonite rod B. an electrically charged cloud C. a current-carrying coil of wire D. a large iron sphere

5. Decide whether each statement is true (T) or false (F). Place your answer in the blank space given.

a. The direction of the field lines of an electric field is either toward or away from

the charged object. b. The direction of the field lines of a magnetic field is toward the field source. c. The direction of the field lines of a gravitational field is toward the field

source. d. The density of the field lines indicates the field’s strength.

6. Match each description with the appropriate term listed. Place your answer in the blank space given.

i. conductor ii. coulomb iii. field iv. insulator v. negatively charged vi. positively charged vii. test body viii. volt a. a characteristic of an object due to an excess of charge

b. a characteristic of an object due to a loss of electrons

c. a material in which electrons can move around freely

d. a material that cannot conduct an electric current well

e. a property of space around a mass, magnet, or electric charge

f. a unit of charge

g. a unit of electrical potential difference

h. an object placed in a region to determine the presence of a field

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7. Explain why water droplets at the bottom of a thundercloud become negatively charged.

8. When drying a synthetic-fibre shirt in a clothes dryer along with other clothes, the shirt gained a surplus of 1.7 ¥ 1013 electrons. Determine the charge, expressed in coulombs, on the shirt. Include the sign of the charge.

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Return to page 5 of the Distributed Learning Student Guide, and begin Lesson 1.2.

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For questions 9 to 12, read each question carefully. Decide which of the choices BEST answers the question.

9. You have studied the relation between gravitational field strength (g) and the distance (r) from the source of the field. Suppose you wanted to describe this relationship by sketching a graph.

Which graph would best represent the relation?

A. g

r

B. g

r

C. g

r

D. g

r

10. Position B is twice as far from the centre of a planet than Position A. A rocket moves from Position A to Position B. How does the planet’s gravitational field strength change for the rocket?

A. The gravitational field strength increases by a factor of 4. B. The gravitational field strength increases by a factor of 2. C. The gravitational field strength decreases by a factor of 1

2 . D. The gravitational field strength decreases by a factor of 1

4 .

11. Suppose two identical balloons are each positively charged and positioned with their centres far enough apart so they are not close to touching each other. The balloons are then moved farther apart so that the distance between their centres doubles.

What would be the expected change in the force of repulsion of one balloon on the other due to their increased separation?

A. The magnitude of the force of repulsion increases by a factor of 4. B. The magnitude of the force of repulsion increases by a factor of 2. C. The magnitude of the force of repulsion decreases by a factor of 1

2 . D. The magnitude of the force of repulsion decreases by a factor of 1

4 .

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12. Assume that the force of the gravitational field strength on the surface of Mars is 3.70 N/kg. An astronaut is standing on the surface of Mars. In his spacesuit he has a mass of 215 kg. What would his weight be at that location?

A. 854 N B. 796 N C. 116 N D. 58.1 N


a. The unit for mass is the newton.

b. Electric field strength is equal to the magnitude of the electric force on a test body with a charge of 1 C.

c. A magnetic field exerts a force on electrically charged objects that are motionless within the field.

d. All moving electrical charges create a magnetic field.

14. Cosmic ray particles can do permanent damage to DNA, especially if both strands are damaged. Explain why damage to just one base on one strand of a DNA molecule may be repairable.

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15. A student’s research indicates that Pluto’s radius is 1.172 ¥ 106 m and its mass is 1.2 ¥ 1022 kg.

a. Calculate the gravitational field strength at Pluto’s surface. Show your work.

b. Calculate the force of gravity at Pluto’s surface on an object with a mass of 100 kg.



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16. A balloon with a radius of 16 cm has an electric charge of 4.25 ¥ 10– 9 C.

a. Determine the electric field strength at a distance of 40.0 cm from the balloon’s centre.

b. A balloon with a radius of 14 cm and an electric charge of 3.75 ¥ 10– 9 C is brought within the electric field of the larger balloon so their centres are 40.0 cm apart. Determine the magnitude of the electric force exerted by this electric field on the smaller balloon.




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For questions 17 and 18, read each question carefully. Decide which of the choices BEST answers the question.

17. Which technological device makes an energy conversion in the same way that a human ear makes an energy conversion?

A. a loudspeaker B. a microphone C. a headphone D. a light bulb

18. Which statement is a reason why a generator can produce electricity?

A. A magnetic field can exert a force on a metal object. B. An electric field can apply a force to a charged object. C. An electric field can make a current in a conductor moving within the field. D. A magnetic field can induce a current in a conductor moving within the field.

19. Match each description with the appropriate term listed. Place your answer in the blank space given.

i. alternating current ii. armature iii. brush iv. coil v. direct current vi. shaft vii. slip rings viii. split-ring commutator

a. the wrapping of wire around an iron core within the magnetic field of a motor or generator

b. a flow of charges that only goes in one direction

c. a flow of charges that reverses in a regular pattern

d. a stationary component of a motor or generator that provides electrical contact

e. a type of electrical contact found on AC generators

f. a type of electrical contact found on DC generators

g. a component that serves as an axis for the rotating part of a motor or generator

h. the complete rotating part of a motor

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20. The failure of a student-built motor during initial testing is usually due to the brush design. Explain why it is important to have the brushes exert just the right amount of pressure.

21. Refer to the following diagram.

After testing this student-built motor, the student saw the armature consistently turning in one direction. Describe two changes in the motor’s design that would cause the armature to turn in the opposite direction.



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22. The output from a current generator is described by the following illustration.

V

t

input ofmechanicalenergy toturn axle

a. Explain why the voltage goes to zero during part of each cycle.

b. Explain why the voltage magnitude peaks during part of each cycle.

23. Give two reasons explaining why electricity generated by AC generators is important to your lifestyle.

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24. Suppose the voltage of the power source in an electrical current is doubled. How will the current’s value be affected?

A. The current will be cut in half. B. The current will double. C. The current will stay the same. D. The current will increase by a factor of 4.

25. The resistance of a circuit is doubled. How is the value of the current affected?

A. The current decreases by a factor of 14 .

B. The current decreases by a factor of 12 .

C. The current increases by a factor of 2. D. The current increases by a factor of 4.

26. Which example is most likely powered by direct current?

A. the glove-compartment light in an automobile B. a household electric frying pan C. the lamp in a kitchen ceiling D. a bathroom ceiling fan

27. A student constructed a simple electric circuit where two light bulbs were connected in parallel. The circuit power source was a 6.0-V cell. One of the light bulbs had a resistance of 25 W, and the other had a resistance of 50 W. What was the combined resistance of the light bulbs in this circuit?

A. 75 W B. 41 W C. 25 W D. 17 W

28. A student experiments with three identical light bulbs. First, he places two of them in series in a circuit. Then he adds a third bulb in series with the other two. What is the effect of adding the third bulb?

A. Each bulb in the circuit will glow less brightly, and the total resistance of the bulbs in the circuit will increase.

B. Each bulb in the circuit will glow more brightly, and the total resistance of the bulbs in the circuit will increase.

C. Each bulb in the circuit will glow less brightly, and the total resistance of the bulbs in the circuit will decrease.

D. Each bulb in the circuit will glow more brightly, and the total resistance of the bulbs in the circuit will decrease.

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a. When measuring a component in a circuit with an ohmmeter, power to the

circuit must be left on.

b. An ohmmeter must be connected in series with the component being measured.

c. When using a voltmeter to measure across two points in a circuit, power to the circuit must be left on.

d. When using an ammeter to measure the current flowing past a point in a circuit, the power to the circuit must be left on.

e. The effect of adding an extra bulb in parallel to a bulb already in a circuit increases the circuit’s total resistance.

f. The effect of adding an extra bulb in series with a bulb already in a circuit increases the circuit’s total resistance.

30. Match each symbol with the appropriate term listed. Place your answer in the blank space given.

i. battery ii. switch iii. joined wires iv. resistor v. lamp vi. ohmmeter a.

b.

c.

d.

e.

f. Ω

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31. Calculate the voltage of a battery made up of four 3.6-V lithium-ion cells connected in series.

32. A 100-W light bulb in a receptacle is supplied with electricity by a residential 120-V circuit. This light bulb draws 0.833 A of current while it is on. Calculate the resistance of the light bulb.

33. Describe how a circuit breaker reduces the risk of an electrical fire in a household electrical circuit.

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34. Explain why the total amount of current flowing through a kitchen circuit and its circuit breaker increases as additional electrical appliances are plugged in and used.

35. A student drew the following circuit.

R1 = 8.00 W

R2 = 5.00 W

R3 = 4.00 W

Determine the circuit’s total resistance. Show your work.

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36. An electric kettle draws a current of 6.50 A while it is plugged into a 120-V electrical outlet. What power does the kettle use?

A. 690 W B. 749 W C. 780 W D. 945 W

37. A test light with an electrical resistance of 9.00 W draws a current of 1.50 A when it is connected to an electrical source. How much power does the light use?

A. 13.5 W B. 20.3 W C. 55.8 W D. 60.7 W

38. Various devices are plugged into a household electrical outlet at different times. Which graph best shows the relationship between the electrical power consumed by the device and the current it draws from the outlet?

A.

Current

Po

wer

Power Versus Current B.

Current

Po

wer

Power Versus Current

C.

Current

Po

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Power Versus Current D.

Current

Po

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Power Versus Current

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39. Suppose the cost of electricity is $0.085/ kWih. What is the cost of keeping a 60-W light bulb on for 141 h?

A. $0.72 B. $1.44 C. $2.16 D. $6.00

40. Suppose a household used 1.65 ¥ 104 kWih of electricity in one year. This electricity came from a traditional coal-fired generating station. Based on the “Comparing Coal-Combustion Technologies” table on page 392 of the textbook, what mass of carbon dioxide gas was emitted to produce the household’s electricity?

A. 1.7 ¥ 104 kg B. 1.3 ¥ 104 kg C. 8.2 ¥ 103 kg D. 2.3 ¥ 102 kg

41. A low-resistance transmitting cable is used to carry 725 kW of electricity from a generating station. If the electricity voltage is 25 000 V, what magnitude of current is flowing through the cable?

A. 5.4 A B. 29 A C. 58 A D. 62 A

42. The following graph represents one cycle of AC current through the primary coil of a transformer.

I II III

t

I

Current in Primary Coil

The secondary coil of the transformer is attached to a light bulb. There are four labelled points in the cycle of AC current through the primary coil. At which of these four points will the magnitude of the current induced in the secondary coil be the greatest?

A. I B. II C. III D. IV

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43. An isolation transformer is a special transformer designed so that its input voltage is equal to its output voltage. Its function is simply to keep sensitive devices electronically separate from the circuit providing the power. If the number of loops in the primary coil of an isolation transformer is 720, what number of loops should there be in its secondary coil?

A. 240 loops B. 700 loops C. 720 loops D. 1440 loops

44. In England, the voltage of residential electrical outlets is 230 V. A visitor from Canada brought along a suitable transformer to run her hair dryer, iron, and other appliances rated at 115 V. If the number of wire loops on the primary coil of her transformer is 1440 loops, how many loops should there be on the transformer’s secondary coil?

A. 2880 loops B. 1440 loops C. 720 loops D. 120 loops

45. The generator at a power generating station supplies the station’s transformer with 23 kV. The transformer steps up the voltage to 230 kV for conduction along a transmission line. When the generator supplies the station’s transformer with a current of 52.2 A, what is the current along the transmission line?

A. 52.2 A B. 10.4 A C. 5.34 A D. 5.22 A

46. A family is deciding which of two freezers to buy. One is a chest freezer that opens from the top. It is rated at using 340 kWih of electricity annually. The other example is an upright freezer that opens from the side that is rated at using 740 kWh annually.

Suppose the average cost of electricity to operate the freezer will be $0.15/kWih.

Over a period of 20 years—a freezer’s approximate lifespan—how much will the family save by choosing the chest freezer?

A. $748 B. $1200 C. $2220 D. $3240

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a. The output voltage in a step-up transformer is greater than the input voltage.

b. The joule is a unit of energy.

c. The kilowatt-hour is a unit of power.

d. The output voltage of a transformer comes off the primary coil.

e. The watt is a unit of power.

f. When the magnitude of the current through a resistor increases, the power consumed by the resistor increases.

48. A 300-W light bulb is left on for 10 h. Calculate the electrical energy (in MJ) consumed by the bulb.

49. A family uses an electric frying pan with a power rating of 1.20 ¥ 103 W. Although the pan is thermostatically controlled, its element was drawing power for 6.30 ¥ 102 min in a period of one month. Calculate the electrical energy in kWih used by the pan during the month.

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50. Explain why ultra-high voltages are used to carry electricity over transmission lines.

51. Explain why a DC electrical source connected to the input of a transformer cannot induce any electricity flow from the transformer’s output.

Submit your completed Assignment Booklet C1 to your teacher for assessment.Then return to page 14 of the Distributed Learning Student Guide,

and begin the Chapter 1 Summary.

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Science 30 U c: e e€¦ · assignmenT BookleT c1 science 30: UniT c chapTer 1 assignmenT This Assignment Booklet is worth 95 marks out of the total 152 marks for the assignments