end of semester exam g12-dec

7/23/2019 End of Semester Exam G12-Dec

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I. Multiple Choice: Encircle the letter of the correct answer.

1. Similarly charge objectsa. attract each other strongly

b. attract each other moderately

c. attract each other weaklyd. repel each other

. !he unit in which the "uantity of charge is e#pressed

a. Coulomb c. $ewtonb. %arad d. &olt

'. If an electric charge is place in a region of space and is subjected to an electric force( this

region of space is recogni)ed as

a. electrification c. an electric field intensityb. an electric field d. an electric field intensity

*. Static electricity is

a. stationary electricity

b. an electric field at restc. produced by friction between two surfaces in close contact

d. both a and c abo+e

,. If you bring a charged object near a conducting surface( you will induce electrons to

mo+e in the materials e+en if there is no physical contact. !his process is calleda. conduction c. induction

b. con+ection d. radiation

-. It is the flow of electric charge that transports the energy from one place to another.a. Current I/ c. 0esistance 0/

b. &oltage &/ d. ower /

2. !he rate at which an electrical appliance con+erts electrical energy to other forms of

energy

a. Current I/ c. 0esistance 0/b. &oltage &/ d. ower /

3. !he property of a material that causes it to oppose the current through it.

a. Current I/ c. 0esistance 0/b. &oltage &/ d. ower /

4. Electrical companies like the &EC5 charge their consumers according to the amount ofelectrical 6666666 consumed.

a. +oltage c. power

b. current d. energy

17. 5ne millionth of a +olt is the same as( which one of these:

a. a kilo+olt c. a micro+olt

b. a mega+olt d. a milli+olt

11. Metals allow electric current to flow through them easily because they

a. ha+e more atoms c. ha+e free electronsb. ha+e hea+ier atoms d. are good conductors of heat

1. 8hich of the following instruments is used to measure and electric current9a. +oltmeter c. ohmmeter

b. electrometer d. ammeter

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1'. 8hen the magnet rotates as shown an alternating e.m.f. is generated in the coil. If the speed ofrotation is doubled

a. the +oltage increases and the fre"uency is reduced

b. the +oltage increases and the fre"uency doubles

c. the +oltage stays the same and the fre"uency doubles

d. the +oltage decreases and the fre"uency is reducede. the +oltage decreases and the fre"uency doubles.

1*. transformer has 177 turns on its primary and 1777 turns on its secondary. If a ,7.;)( 177. &

output is seen at the secondary( then the

a. fre"uency at the primary is ,.7 ;)

b. +oltage across the primary is 17.7 &

c. current in the secondary is 17 times the current in the primary

d. secondary dissipates more energy than the primary

1,. !he unit for electrical power is the

a. joule c. ohm

b. watt d. $ewton

1-. !he current direction in the rotating coil of a simple d.c electric motoris re+ersed e+ery half

re+olution to

a. re+erse the polarity of the field magnet

b. pre+ent corrosion of the brushes.

c. maintain the direction of rotation of the coil

d. pro+ide an a.c output from the motor

12. 8hich of the following statements is


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1. !he diameter of a proton is of the order

a. 17=4m

b. 17=11m

c. 17=1'm

d. 17=1,m

. In 1474( >eiger and Marsden carried out e#periments in which a thin gold foil was

bombarded with alpha particles. 8hich of the following could be deduced from the results

of their e#periments9

a. !he nucleus of an atom contains both neutrons and protons

b. Electrons in an atom can only ha+e certain energy +alues.c. !he positi+e charge carried by the atom and the mass of the atom is concentrated into a

+ery small region within the atom.

d. Electrons are much less massi+e than protons.

'. !he nuclear notation for lithium=2 is '?i. 8hich one of the following is the mass oflithium=29

a. 17 g c. * gb( 2 g d. ' g

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II. Essay: E#plain your answers to the following "uestions.

1. a/ 8hat structural characteristics causes an object to ha+e a positi+e charge9 pts/666666666666666666666666666666666666666666666666666666666666666666666666

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b/ 8hat is the basic law of electrostatics


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b. fter this( the two balls were touched with the end of the glass rod that was

positi+ely charged. !he glass rod was repelled. E#plain also this obser+ation.

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c. 8hich terminal positi+e or negati+e/ of the battery was the wire connected9

E#plain your answer briefly. ' pts/666666666666666666666666666666666666666666666666666666666666666666

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III. Sol+e the following problems. Show your solutions. Ase the correct number of

significant figures and correct cancellation of units. Each item is more than * pts/

1. young woman accumulates a charge of q1of .7 # 17=,C while sliding out of a front

seat of a car. ;er boyfriend( who has been waiting in the wind( has gained electrons and

now has a charge q2of =3.7 # 17=,C.

a. Estimate the magnitude of the electrical force that each person e#erts on oneanother when separated by a distance of -.7 m. Is the force attracti+e or

repulsi+e9 * pts/

b. Suppose the two people mo+e toward each other. Calculate the magnitude of the

electrical force of one on the other when their separation is reduced by a factor of7.,. * pts/

. a. If an automobile starter a has resistance B of 7.17 ohm( how much current flows

through the starter when it is connected to a 1=& battery9 ' pts/

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b. ;ow much charge passes through the starter if it runs for 17.7 seconds9 pts/

'. 0efer to the following diagrams. Each indi+idual resistance is -.7 . nswer by using

the letter below the appropriate diagram.

a. !he resistance combination ha+ing the largest total resistance. 66666

b. !he resistance combination ha+ing the smallest total resistance. 66666c. !he resistance combination ha+ing a total resistance of *.7 . 66666

d. !he resistance combination ha+ing the total resistance of 4.7 . 66666

*. Estimate the e"ui+alent resistance of the Dladder of e"ual 177 resistor as shown in thefigures below. In other words( what would an ohmmeter read if connected between

points and F9 , pts/

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,. '7.7 resistance is connected in parallel to a 1,.7 resistor. !hese are joined in

series to a ,.77 and a source with an emf of '7.7 &.

a. Graw a circuit diagram. pts/

b. Calculate the total resistance. ' pts/

c. Calculate the +oltage drop across each resistor. , pts/

d. Calculate the current in each resistor. , pts/

-. 17.7 & battery whose internal resistance 0 is 7.*7 is connected in the circuit as

shown below.

a. ;ow much current is drawn from the battery9

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b. 8hat is the terminal +oltage of the battery9 pts/

c. 8hat is the current in the 2.7 resistor9 ' pts/

2. piece of charcoal known to be appro#imately ,777 years old contains 2.4- # 1717C=1* atoms.

a. Getermine the number of decays per minute e#pected from this sample. !he half=

life of C=1* is ,21, years/

b. If the radioacti+e background in the counter without a sample is 7.7 counts per

minute and we assume 177.7 percent efficiency in counting( e#plain why ,777 is

close to the limit of dating with this techni"ue.

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end of semester exam g12-dec

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