4 dc electricity test 11_12 answers

8/2/2019 4 DC Electricity test 11_12 answers

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AMERICAN AeA6 PHYSICS: SEMESAdvanced Level - ASUnit 2: Physics at Work:Time: 1 hour 20 minutesIWrite your name here

, I SurnameWrite the date here

' I You must haveScientific calculatorRuler

!"Instructions

Use black ink or ball-point pen (hlackfhlue). Fill in the hoxes at the top of this page with Answer all questions (there are 20 questions Answer the questions in the spaces provided In calculations you should show all the stepsInformation The total mark for this paper is 71 (+ 8 chall The marks for each question are shown in br.on each question, Questions labelled with an asterisk (*) heforof your written communication will be asses

punctuation. and grammar, as well as the clarit Questions with an asterisk (*) after the nummore searching and deeper and it is intendedphysics. They are honus questions and you s The list of data, formulae and relationships is You may use a scientific calculator.

Advice Read each question carefully before you star Keep an eye on the time. Try to answer every question. Always check your answers.

DEMY LARNACATER 2: TEST ITopic 4 -;-DC electricity

I Other names

GRADE

your names and the date.and 1 challenge / bonus questions).- there may be more space than y.oU need.in your working, giving your answer at each stage.

enge / bonus marks).ackets - use this as a guide as to how much time to spend

e the number of the question, are ones where the qualitysed - you should take particular care with spelling,y .of expression, on. these questions.ber of the question are challenge questions. They areto challenge your knowledge and understanding ofhould attempt them only if you have time.provided separately.

t to answer it.

Turn over


2/15

-2-Questions 1-10: Choose the right answer from choices A, B, C or D.

: 1 . ' During a thunderstorm, a flashof lightning resulted in 600000 C of charge flowing in a~ lightning conductor in a time of 40 ms. The current in the conductor was

0 A 1.5 x 104 A 1.-::: Q . - = - b 0-0 (jU"() Cle -D- B 2.4 X 104 A ~O""'-~ 4! & 1 C 1.5 x 107 A : ; ; . \.s ~ U,) A-D D 2.4 x 107 A

~ The unit of potential difference can be expressed as0 A C S-1~ B J C-10 C An-10 D JA-1

~ A steady potential difference is applied across a variable resistor that is kept at aI constant temperature..'. ]'[\ ][\ 1 1 /~I ~ 1/00 R 0 R R 0 R

A -B C DThe graph which represents the relationship between the resistance R of the variableresistor and the current] through it-is~ Ao Bo Co D

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3/15

-3-A student wants to find the internal resistance of a cell. He plots a graph of the potentialdifference across the terminals of the cell against the current through the cell.

Potentialdifference / V

o 3 42 5Current/ AWhich of the following quantities gives the internal resistance of the cell?o A The area under the graph.D B The intercept on the current axis.o C The intercept on the potential difference axis.I 5 ? l D The magnitude of the gradient.A negative temperature coefficient thermistor is connected as shown in the circuitdiagram.

The cell has a negligible internal resistance. The effect of decreasing the temperature ofthe thermistor is-that theD A ammeter reading will decrease.l X J B ammeter reading will increase.D C voltmeter reading will decrease.D D voltmeter reading willincrease,

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4/15

-4-6) Three identical resistors are connected across a potential difference V so that one of them-;; is in parallel with the other two which are connected in series. The power dissipat~d

through the first one, compared to the power dissipated by each of the other two, ISapproximately

/'f':; T. . if ;: IYo .A the same T . ::i"i.. 1t

o B halfasmuch ----o-=-~~o C twice as much ~';~~J :~-.l~ D four times as much l.. ~. &V --, " '? - = " ' G /

~ Two wires of the same material are connected in series in the circuit shown.WrreX WireY() I ,

The cross-sectional area of wire X is twice the cross-sectional area of wire Y..The drift velocities of the electrons in these two wires are Vx and Vy.The value of v x _ IS

Vy

18 A Y zo B 1o C2o D4

::: \- -

The resistance of a length of copper wire is 6 O. A second piece of copper wire hastwice the length and twice the cross-sectional area. The resistance of the second pieceof copper wire is0 A30 \Z=~~ 0 < . . . l ~ 2..\.. L:::- - -~ B 60 A " " 2 . . . A ~0 C 1200 D 240

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5/15

~ A circuit is set up as shown in the diagram.

100-:':

/~I q -I 400 --I 200 --~ \'


6/15

-6-j 1 ) The circuit shows a battery of negligible internal resistance connected to three resistors.

4 n 0.75 A-

19 .0 V : R 2 4 ! 2~T T J,2

-- .

Calculate current 11 ,

.t .

(3 marks) iCalculate resistance R.

Q : : : v . - 9: 1 : - - ~ A > < . : = z . : ~ J L-I Cl' - : : r 5 A . - o- J .> AR= l~

(2 marks)(Total for Question 11 = 5 marks)

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7/15

-7-~ The power supplies in the two circuits shown below are identical,

I

+vR ,

IIlf[,

Write down the relationship between 1 1 , 1 2 and Iwhich must hold if the combined resistance of theparallel pair, RI and R2' is to equal RT'

1..::: "t ~"\............... ...-.\ ~ . . , : .(1mark)

Hence derive the formula for the equivalent resistance of two resistors connected in parallel.

............ V ;:: V - ' s ' V . .. .

. . . . . . . . . . . . ~~ ~ ~ ~"\- ..\ ~ \ -\- ~............. ~ ~ .\2-., \< , R__ (~rnarks)

Use your formula to show that the resistance between the terminals of a low-resistance componentis hardly changed when a high-resistance voltmeter is connected in parallel with it.

.... ~~.::: ..~~~~ ..~ ..~.~ ..

. . . . : c ? ' \ - . : = - . . . . . ' ' ; . . . . . . . . \ \ . . . . . .0.......I...i'--C.\\ol.l~ .~ ... ~':I:' r ''?:\ ' .

.~.\:r.\\ .. C i1 . l . :> : 1.. ~ .. ~ .R.~ R\ ~,--'(J,marks)

(Total for Question 12 = 6 marks)

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8/15

-8-

Use the axes below to sketch and label two graphs to show how the current varies withpotential difference for (i) a metal wire, and (ii) a semiconductor diode, both at constanttemperature.

I I

v v

( , . 2 . .marks)A semiconductor. diode carries a current of 20 mA in normal operation. The potentialdifference across it should be 1.9 V. Complete the diagram below to show how, with theaddition of a single component, the semiconducting diode may be powered from a 5 V supply.

5V

(j mark)Calculate the value of the additional component required .

. . . . .'R.: . 1 o : \ V .- - -- : ; 2 . .0 .A .Value of additional component = . l?? . S l . . - - . . . . . .

-(3 marks)


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9/15

-9-~ - - - - - - - - - - - - - - - - - - - - . - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - ~The battery in the circuit below has an e.m.f. of 5.4 V and drives a current of 0.30 A throughthe lamp.

5.4 V Lamp0.30 A

(a) On the circuit above, label the voltmeter and the ammeter. (1mark)(b) The voltmeter reading is 4.8 V. Explain why the voltmeter reading IS less than the

e.m.f. of the battery. ". ~~~~ ~~ .~~~ .. ~t:?~

., '. ~ .. \':>.!A..-. ~:~: .. ~~.~ .. ~ .. ~.~J.:- ..~n~uc--(2 marks)

(c) Calculate the internal resistance of the battery.v ~ . ~ - .1;. '( ' .. .~ .If. . ::: . E :-v .:: :. . t ; . A c V . - : - .+. .W.~ --------.... . . ~: O ~.o.A.

Internal resistance = . .").:0 .S!-r .- (3 marks)

(d) Calculate the energy transformed per second in the lamp.

Energy transformed = t4-~.\.Y ._.=--= (3 marks)(e) State two assumptions you made in order to complete these calculations.

1 .A . .. . k ~ . v . - o . . ~VJ~. . ..2 .V . ~ f f l . . . ~ . ~ ~ . .

(2marks)


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10/15

-10-

A very high resistance voltmeter reads 20V when connected across the terminals of a d.c. powersupply. The high resistance meter is disconnected and a second voltmeter of resistance 1.0Wis then connected across the supply. The second meter gives a reading of 16V.(i) State the e.m.f. of the power supply .

........................ .(ii) Calculate the current which flows through the second meter ......................:G :l 2. .\.~v. ::: .\.~~A .- - -R. ~OI.::-fL.,(iii) Calculate the internal resistance of the power supply .

. . . . . . . . . . . . .. .. .. . ..[ . .: : y . ? t . v . : _ _ ~ k ..?-.Q .R ... _ .- - -====="'1 It....

(iv) Show that the current is equal to 0.080 A when the supply is.short circuited ....................~::g :: ~II. ::: $Q.~~ ,.. .

(" 250.11 .....


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11/15

-11-A piece of insulated electrical wire has a resistance of 18 ,Q. As shown in thediagram below, it is cut into three equal pieces X, Y and Z (each one third thelength of the original).

18.Q

x Y zDraw diagrams to show how you would connect X, Y and Z together to producea total resistance of: (a) 2,Q, (b) 4,Q, (c) 9,Q . Justify your answers. [6]~

0 > - ) 1 : l - .. L ~ 1- ~i. It-- 1 - ::;. ").\" L b ~ ~ - b' Z . . :;: 2..JL~) t"l.rt..$ r eS :J-- Q.. . = - i -\- ..L--[~ - \L \-V "- ':: . 1 - J . . "L ::::>C o l t - - ~ ( " t . , \ " 1 . . . - tt.

R . " I : . +..1\ . .

c"') ~[: J loA ' - r t . .m m ::: -c::l-c::J;--- R= 'fJL(Total for Question 16 .i. 6 marks)

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12/15

-12-A student wants to provide lighting for a model house which she has made. She needs3.0 V for her lamps but only has a 9.0 V battery, so uses a linear resistor AB in thecircuit below. The linear resistor is made from a high resistance uniform conductor.

l~iding contact

(3)

Linearresistor9.0V :V

What is the name of the device AB when it is used in this manner?................tlk.\\.9..~~~ : .

(1)State the voltmeter reading when the sliding contact is at:

A C f O V......................................... oo-/ .(2)

The student moves the sliding contact until the voltmeter reads 3.0 V.Add an arrow labelled X to the diagram to show where the sliding contact must beplaced. (1)The student replaces the voltmeter with a 3.0 V lamp but the lamp does not light.Explain why the lamp does not light..............~ ~~l~~.).~~ ..................~ ~.~ ~ ~.~ ~~ R ..~ ~J. .... ....... .. ... .J(S1 5>~ ~~ \A ~ ~~ ~ -.f .!.Q.lL: J___ ___~_ . . . . . . .. . . .. . . . . . . . . . . . . . . . . . .. . . .. . . . . "~ " . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . " ............................................................................................................................................

............................................................................................................................................

(Total for Question 17 = 7marks,l

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13/15

-13-1S ) The diagram is a velocity-time graph for an electron.

vB/ / /

(2)

1/ [7 VvA c

(2)

( 1 )

Describe carefully the motion represented by lines AB and BC.AB: ~~~~ .............................................................................................................................................

BC: l.~~~.~~~~~ ............................................................................................................................................ (2)The graph is a much simplified model of how an electron moves along a wire carrying acurrent. Explain what causes the motion represented by AB and BC.AB: ~\~ (A,,~~b ~.>. b.~.~ ............................................................................................................................................BC: ~t\D..~ ~.\..\~ \ l . M - > . ~ . ~ ~ . : . s . ..............................................................................................................................................

Explain the term drift velocity and indicate its value on the graph above ..........~\..~ ~.\~~~ ;:;. ~.~ 'r!?~~~ ~ fLt.S .

... ---_ _ _ ._-_ ..- -----_ .._ -_ ..._ -_ .._ _ .._-- -._ .._--_.___ _ ._-----_.. _ .._- c

With reference to the behaviour of the electron, explain why the wire gets warm ........... .C4~\:V.i..~ ":-!-!.~~ ~ ~~ F ? . \ .~ J 0 : ' x c . "E\,:::::" , . 0

...........................................................................................................................................


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14/15

-14-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

(Total for Question 19 ~ ~marks)

Three sealed opaque boxes are known to contain components as shown. Each box has twoterminals on the outside. The values refer to the normal operating conditions and allcomponents can safely carry a current of 0.30 A.

200

You are provided with the usual laboratory equipment. Explaining how you would reach yourconclusions, describe experiments which you could carry out to identify

the box containing resistor only, 1 Z . ? . .V . ~ ~ ~ .~ ....... .......... ........................ ......... ..... ......... .. .... ... ~ ... ............ ................. ... .. .. ....... ........... ..... ... .................... ............. .. ....... .. ..... .... ...... ... .. .. .... ........ ...... .... ... .... ..... .. .. ............. ......... ........................ ..... .................. .. ......................... V the box containing a bulb, R . : : : i ?~~~ .I................................. .............. ............................................ ...................................................... ............................................................................................................... .t':.;q ...I:...... ............................... ........... ............................... .. ......... ............... ... ................. .. ............... ....... .. ... .the box containing a diode ~~}? ..~.~.:, R.? . ~ : ' ? : ' k~.A.- .r.. ...... ............................ ............ .. ... ..... ... ... ..... ....................................... ... .... ............... ................. ...........................................................~ ~.~~ ..:....~:"!':" ~ : : : ! . ' ~ .l'----------- ------. -.-....-.-........._........-- ..-.-"--.~..!...~.-=-.:.!..!.!.~...!~::.!!~~~.-:.:.:..:. .:..:.~

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15/15

-15-, ,~+1\ 1 : " I " , . . \ - r , J' L1!A B-,.- R = 050 --20V 18V0250 T 030

Two cells A and B with emfs and internal resistances as shown are connected in parallel with aresist-OfR of value 05 O. Find the power produced by each cell and the power dissipated in R.Comment on your answer.

1..oV _ - ( 1 , a ., .Tt\') 'l O < ; R. - ( T A . 'X. Q. :lSSl-) ::: 0 < :1..-v\/ - ( 0 1< ;'.st.. '>' - . r ~ ) ~ ( OS-..&. >c:: C3) ' = ' Q - C 9--~?...oV - \$V k ( In 'x. o - 1JL) - (~x Q' 2SIL) ~ ()'-O'2V - ( (J'J." TJ< ~o') :::.()

T~ ~ \A ... . . . .. ~ - - - - ~- ~ __ 0 ____ - ----- ---~--------- ---------- - - ----- - --- .. . . . . . . . . . . ,f' ":: 1:~~ -:; " '-0\1 = = ' ~V I ' ! . ; ; ; 1 : ' 0 ,..:\-~V :;; :' \-I{W-.?~-::.C rb -~1:~ ~ x O Sfi--. ; ;: ; . A-' s.vJ;;::==;-( ? 1 '" le - '?~\ c:: \? \&~ ~wr= ~~~"'Y.. \.~'- tt. \..:.~..k- ~\-:.\.,....~ (Total for Question 20 = 8 marks)11_-_

4 dc electricity test 11_12 answers

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