y6/as physics final exam 11_12 unit 2_answers

7/31/2019 Y6/AS Physics final exam 11_12 Unit 2_answers

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AMERICAN ACADEMYLARNA ;CA.- ~ -, .- _.FINAL EXAMINATIONS 201~1 12" - " -PHYSICS ,Year 6 [Advanced Subsidiary]

" Unit 2: Physics at Work IFriday 27 April 2012 - 9.15 a.m. Paper ReferenceTime:Ihour 30 minutes PH02/01

- ' ~ "Teachers A. G. Chimonides / P. BurgessNo. of students 10- - - , ,' -Write your name here

Total marksoumust have:ScientificcalculatorRuler

I,;t~~~ ~ ~,_-~-,----~-~-------W',

Instructions Use black ink or ball-point pen (blacklhlue). Fill in the boxes at the top of this page with your names. Answer all questions (there are 22 questions) . . . . Answer the questions in the spaces provided - there may bemore space than you need.Information The total mark for this paper is 80. The marks for each question are shown in brackets - use this as a guide as to how much time

to spend on each question. Questions labelled with an asterisk (*) are ones where the quality of your writtencommunication will be assessed - you should take particular care with your spelling,punctuation and grammar, as well as the clarity of expression, on these questions.

The list of data, formulae and relationships is printed at the end of this booklet. Candidates may use a scientific calculator.Advice Read each question carefully before you start to answer it. Keep an eye on the time. Try to answer every question. Check your answers if you have time at the end.

Turn over


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II'I1I- I

' ' 1 , ~ ~ ~ ~ ~ . . _ _ : . . ~ : . ; . . . . . ; . . .. . J . . . . _I (Total for Question 1=1 mark)I 2,

I

SECTION AAnswer ALL questions.

For questions 1-10, in Section A, select one answer from A to D and put a cross in the box~.U you change your mind, put a line through the boxSnd then

mark your new answer with a cross ~.A child's toy is operated by a small motor. The potential difference across the motor is6.0 V and the current in it is 0.20 A. The energy used by the motor in 120 s is0 A 2.401 ~= T.V.k0 B 60.01 ' : : 0 o 2 ..o A ~ ~ .o v ')c:" \?...O S .~ C 14410 D 36001

Which one of the following does not apply to sound waves?0 A They transmit energy.~ B They travel faster in a vacuum.0 C They result from vibrations.0 D They are longitudinal waves.

(Total for Question 2 =1 mark)

1 3 Two coherent sources emit waves of wavelength A in phase. At a point where the twowaves meet they have a phase difference of 90 ( - i radians). Which of the followingcould be the path difference at this point?

o A 2 . . 1B A

o C!2

I1 -I.. .. . . . . ." " .

D A4

(Total for Question 3 = 1 mark)------,--------- -----------------~------~.

~ ... ./3

1

II SII


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I

III

The four diagrams show waves of different wavelengths approaching slits of differentwidths.

A

o A~ Bo Co D

I IB

In which diagram will the diffraction be the greatest?

IcI

D

(Total for Question 4 = 1 mark)

o A Y-.R

IIi 5 The heating element for an electric fire is made from a wire of resistance R. It isI replaced with a wire of the same material which has the same length but is twice the! diameter. The resistance of this second wire isII B YzRo C 2R

il. D D_ _ 4 _ R ~ ~ ~ _(Total for Question 5 = 1 mark)I!IIl . . G -,.

1


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6 The diagram shows some of the electron energy levels for the hydrogen atom with fourpossible transitions.

-0.8~ - - - = - ~ - = - ~ ~ - - - - - - ~ - ~ -- - ~ ~ ~ ~ ~ - ~ - ~ ~ ~-1.51 ----- ----- --------~---------Energy I eV

-13.6 --- --_.--

A B

The transition that would result in the emission of the longest wavelength is

(Total for Question. = 1 mark)

o Ao Bo Crg ' D

f Ultrasound pulses are used to detect shoals of fish in the sea. A shoal of fish is at adepth of 300 m and the speed of ultrasound in water is 1500 m S-I. The time intervalbetween transmitting and receiving the pulse will be0 A 0.20 s \ ( - = - s -: ;? k = S :; ~0tJ ..- -~ -B OAO s V- ( . s . U V " < A ~ , \ .0 C 2.5 s

'"" 0 D 5.0 s(Total for Question = 1 mark)

." 'S


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~ The graph shows the displacement of molecules against their distance from a wavesource. Which of the points A to D, marked on the graph, has a phase difference of 2700with point X?

displacement

X


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10 Two wires of the same material are connected in series with each other. Wire A hastwice the diameter of wire B. In which of the following rows are both statementscorrect?

current in wire A drift speed in wire A .current in wire B drift speed in wire B

~ A 1 1-40 B 4 1 4

0 C 2 4

0 D 2 1-4

(Total for Question 10 = 1 mark)TOTAL FOR SECTION A =10 MARKS

. . . f

=


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-:f-SECTIONB

Answer ALL questions in the spaces provided.11 A cell of e.m.f. 1.5 V is connected to a lamp of resistance 80 O. The current in the

circuit is 1 7 mA.Calculate the internal resistance of this cell.

~::1.(f~+~) ..C - = = : ~ . . . .: - : -. . . .~I

r--.;:.r " " " . .. . . . . ., .I ~~~~~~~.. ~.~~~

=~ Uf)O..A..t-sv0..J


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1 ' 3 Noise cancelling headphones were first invented to cancel the noise in aeroplane andhelicopter cockpits. They work using the principle of superposition of waves.

Sound waves enter and pass through the headphone and are detected by a microphone.An electronic circuit sends a signal to the loudspeaker so that it produces an 'oppositewave'.

Microphone

\MILoudspeaker

(a) Compare the properties of the two sound waves necessary to produce completecancellation of the two waves that reach the ear.

(3)

...................................................................~.~ k,~.~ .\'- ~\l ..~ ...w ..... . n ~ ~ f(.~~ .

....?


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*/If A student carries out an experiment to measure the refractive index of glass. She does thisby shining a ray of light through a semicircular glass block and into the air as shown.

y

x

(a) Calculate the refractive index from air to glass allg.(2)

< 7 . , .. A- . ;; .; ; . ;; : . . "\ . :;'>.~~tS o " " ,- >0"

Refractive index = .. L~?......(b) (i) The student steadily increases the angle x in glass and finds that eventually

the light does not pass into the air. Explain this observation.(3)

..'Vkx>.c... = - , ~~~~vW-: ~ .;") .~~\~"'~~.~~~\.~

(ii) Calculate the largest value of angle x that allows the light to pass out of the- block into the air.

(2)

Angle = 'T - - r-(Total for Question 1 '1 = 7 marks).. '/f


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- 1 / -r ..iI * /5 A student looks at the sunlight reflected off a puddle of water. She puts a polarisingI (Polaroid) filter in front of her eye. As she rotates the filter the puddle appears darkerI " then lighter.I Explain this observation ...........................~~,~ ~9..\..~~ l~~ t ;.~~ \M ,~ ~ \~ 1 .

i ~ ~'?\~~ ~.\~ ~h~ ~.~ ~ ~\~ .I . . . . .\~\A \o ~~ w~ ;\ ~ ~ .1 :~"7~\..~"" '~ - .

I .! (Total for Question. = 3 marks)

, The current J in a length of aluminium of cross-sectional area A is given by the formulaJ= nevA

where e is the charge on an electron.(a) State the meanings of nand v. '''''),\ .

n: ~c.~ ~..~ ~.~~ \ro\.A..~..................................... ~v: td.R...c~~ c l& - \ . k ~.b.~ .

(b) Show that the units on the left hand side of the equation are consistent with those onthe right hand side.

(3)I .I ~ "'.g,...\r...~ .II ~ : : :~~?.C ~..~.~'~~ .ii .: A . ~ C $ . . - : : ' .I -A - : A I .i .I . .. . . . . . .. . . . .. .. .. .. . .~-.--==~~ . . 7/2


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/ (;, The circuit diagram shows a battery of negligible internal resistance connected to threeresistors.

O.60A

(2)

(2)

(2)

---r9.0VI I--L- R 30Q

(a) Calculate the potential difference across the 5Q resistor.

......~..I.~.? O:~QA )<


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F / An integrated circuit uses strips of gold as connectors and strips of silicon as resistors.A strip of gold of cross-sectional area 3.0 x 10-6m2 carries a current of 8.0 mA. Thecharge carrier density n is 6.0 x 1028m".(a) Show that the carrier drift velocity v for gold is approximately 3 x 10-7 ms.

(2)"::.~~()~\Q~::'" ..

(-0,)(, \ u " z " " ' " \ . N \ . - > ' ) ( ' 1-0...c'\O -Co .y . ." ' \ . ,>


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/ B A child wants to power his model train set from a 12V battery. He also wants to be ableto control the speed of his trains.His sister is studying Physics and suggests using the following circuit.

.~ l x Sliding contactT


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(Total 9 marks)

(b) (i) She chooses a carbon rod. Explain why this is a good choice ...........t ~ ~ ..rt ~ I...~ ;) - t '. Q . ~ .......................... .... ...... ...... ................................ ..... ........ \~.).~ ~ .............................................................................................................. " .

(ii) The carbon rod she uses has a cross-sectional area of 3.0 x l O - - 6m2 and a lengthof 40 cm. Show that the total resistance of the carbon rod is about 2 Q..........~~\,. ~ \.1~lO~.~R~ ').(..9.:AQ~ .A l,."() \()- b '"'"'-.................................l~.~A .

(3)(iii) Assuming that the internal resistance of the battery and the resistance of the

comiecting wires is negligible, state the potential difference available to the trainset when the sliding contact is at:x \~v. . y Q . v .

(1)(iv) The total resistance of the wires connecting the battery to the resistor is about

0.5 Q. Explain whether this would have a significant effect on the potentialdifference available for the train set. i~ .

. . . . . . . . . . . . . . . . . ~ ~ 9 . : . 5 - , J L . ~v. \- ~ S:~~ ~.~

................t.tA = : ) ~b~.~~ ~ ~~ ~A...X ,....... .... ...... ~~ \ .

(2)

(2)


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-/6-* 1 9 I n 1921, Albert Einstein won the Nobel Prize for his work on the photoelectric effect.

n The results of experiments on the photoelectric effect show that: photoelectrons are not released when the incident radiation is below a certain

threshold frequency; the kinetic energy of the photoelectrons released depends on the frequency of the

incident light and not its intensity.Explain how these results support a particle theory, but not a wave theory of light.

.........~ ~ ..k~(oJ:> ~.(J-v:~~~ ~i .."\.\.~ ~ ~ ~. .~~u~~~~'-f2Mp"7\~6\\\~\.e ~.LR....J&

.........s.v.y.-.~~ ~~~ .

..... tl\:7~~~~ ~. . .nE t- c . l ( 2 . . . ~ ~ .... ~...~~~\~t ~ ~ ~.~...~()b~ ~ ~..~ .It-~s:ve\~~ ~...E~.~~

(Total for Question 19= 6 marks)


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-/7-10 The graph shows how the maximum kinetic energy E of photoelectrons emitted from the

surface of aluminium varies with the frequency f of the incident radiation.

3

104=~==+=~~U=~~~~=4~~4o 64 8 10 12 14 16 18 20

(1)

(3)

- ~~.~.y.\Q~\~).. . .\ . < . . Y to -\~"S Q. V -,

i~

Work function = 1.\..~V .(1)

(2)

(a) Explain why no photoelectrons are emitted below a frequency ofl0 x 1014Hz.

(b) Calculate the work function of aluminium in electron volts.

(c) State the quantity represented by the gradient of the graph.

...............................................(d) Add a second line to the graph to show how E varies withf for a metal which has a

work function less than aluminium.

(Total for Question . to= 7 marks)

. V~


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r 2 . f The diagram shows a difuacti~n pattern. \

(a) Explain what is meant by diffraction.(2)

1f~c...~~ ~ ~....~~ .......~ ~...t?4.h\.~ "i~\.~-l~~~

(b) This diffraction pattern is produced by electrons passing through a thin sheet ofgraphite.

Ii) State what this suggests about the behaviour of electrons. (1)(ii) Suggest why substantial diffraction occurs.

(1)

(Total for Question Z (=4 marks)


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BLANK PAGE


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-1,0-21 Warning traffic signs that tell motorists they are speeding are often solar powered.

The speed of an approaching car is measured by transmitting microwaves towardsit. These waves are reflected off the car and picked up by a receiver, which uses theDoppler effect to calculate the speed of the car.(a) A narrow beam of waves is necessary to pick out a single car. Suggest a reason why

microwaves are used rather than radio waves.(2)

...............~~'Y~~~S~~A ~.Vt..,~~ .. . . . . . . . . . . . . . . . . . . . . Q ~ b.\().I\., ~~~\O

(b)(i) State how the frequency of the reflected signal would differ from the frequencyof the transmitted signal.

(1)......\~hvv .

(ii) Explain how the system detects that a car is speeding.(2)

......................... ~ ~.~~....... ~~ ~ ..~ ~ .....~ ..~ ..~ ~ ~ .

.. -/2.(


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-1./-(c) If a car is speeding, the warning sign flashes to alert the driver. The warning sign

is powered by solar cells covering a rectangular area 0.5 m x 0.3 m. The averageintensity of the solar energy radiation hitting the solar cells is 500 W m-2. The solarcells are 8% efficient at transforming light energy into electrical energy, which isstored in a battery.(i) Calculate how much electrical energy is produced each second by the solarpanel.

(3)...................s.'O~1~)xY;

l0"D

Electrical energy each second =6\.V................(ii) The panel receives solar energy for 8 hours per day. The warning sign requires

100 J of electrical energy each time it flashes.Calculate how many times the warning sign can flash in a day.

(3)~~ ..)( .. \~ . ..J,bOO..S .) .

lro - : : >

Number of flashes =ttQQ(Total for Question . 2 . . 2 . =11 marks)

TOTAL FOR SECTION B = 70 MARKSTOTAL FOR PAPER = 80 MARKS

~ . '2Z


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List of data, formulae and relationships

(close to Earth's surface)= 9.81 m S-2e = -1 .60 x 1O -19Cme = 9 .11 x 10-31kg

1 eV = 1.60 x 10-19Jg = 9.8 1 N kg:'h = 6.63 X 10-34 J sc = 3.00 x 108m S-I

Acceleration of free fallElectron charge

! Electron massI ElectronvoltI Gravitational field strengthPlanck constantSpeed of light in a vacuumUnit 1I Mechanics. Kinematic equations of motion

(close to Earth's surface)

v =u + ats = ut + "hat2v2 = u2 + 2as

Forces 'L .F = mag=F/mW=mgf..W = FtssE = "hmv 2kM = mgtsh .gra y

Work and energy

II Materialsa Stokes' lawHooke's lawDensityPressure

F = StcnrvF = ktsxp = m/Vp =F/A

Young's modulus E = a/e whereStress (J =F/AStrain s = !ix/x

Elastic strain energy

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1.,

i-t Unit 2. Waves

Wave speedRefractive index

v=flIJ1 2 =sin i/sin r =v/v 2

ElectricityPotential differenceResistanceElectrical power, energy andefficiency

V= W /QR = V/Ip= VIP =J2RP = V2IRW= VIt

useful energy output% efficiency = ------=:;;~----"'--x 100energy input

% efficiency = useful power outputpower input x 100

ResistivityCurrent

R = pl/AI= I'1Q/l'1 tI= nqvAR =R I + R 2 + R 31 1 1 1-=-+-+-R R I R2 R3

Resistors in seriesResistors in parallel

I Quantum physicsI11 . Photon model

Einstein's photoelectricI equation

I

E=hfhf= ~+ Yzmv2max

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y6/as physics final exam 11_12 unit 2_answers

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