Planning Experiments QP 2

8/6/2019 Planning Experiments QP 2

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LeaveQuestion C blanklou are to plan an il1\'estigation of how the resistive property of an a.c. circuit, called itsimpedance, depends 011 the frequenc}' of the a.c. supply. You are then to analyse a set ofdata frol71 sllch an experiment.(a) (i) In a preliminary experiment a 47 flF capacitor is connected in parallel with aresistor of nominal value 100 D. They are connected to the a.c. output of alaboratory power supply, with an ammeter to measure the current 1 in the circuit.A \oltmeter is used to measure the potential difference V across the resistor

capacitor combination. Draw a circuit diagram of this arrangement.

When the p.d. was 1.50 V the CUITent was found to"be 26.0 rnA. What value doesthis give for the impedance Z where Z = V/ f'?....... .. . .... .... . . . .. . .. .... . .. . . . .... .... ...... ...... .. .. . .. .. . .... .. .. .... . .... .. . . . . . . . . .. .. . .. . .. .. .. .. . .. . .... .. .. . . .. . . . ..

... . ... .. .. .. .. ... ... .... . ... . .. ...... ...... ........ ... ........... ... .. ......... ..... .. .. .. . .. .. .... .......... .. . ..... ... .. ... ..... (3)/

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June 2003 (International)


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(ii) For this circuit1 _ 4 2f2C2 1-- 1t +Z2 R2

where f= frequency of a.c. supply = 50 Hz R = value of the resistor C= value of the capacitor.

Calculate the value of Z given by this equation . .. .... .. ...... ... .... ....... ... ... ... ..... .... ... ..... ... ... ... ...... .... ...... .... ..... ........ .... .. ..... . . .. ... ...... .... .... ...

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

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

.. .. ....... .. ... .. .. ...... .... .... ....... ..... ..... .... ... .. ...... ... .. .. ....... .... .. .. ... .. ..... ........ .... . .. .. ... .... ....... .. (2)(iii) Describe briefly how you would investigate the equation in part (ii) experimentallyfor different values off Your description should state any changes you wouldneed to make to the apparatus and should explain why a graph of 1/Z2 againstf2

should be plotted.... ... .. ..... ... ............. ..... .. .... . ..... ......... ...... .... .. ... .. .. . .. .,..... ... .. .. ... .. .................... .. .. . .... ....... ..

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

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

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

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

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

(4)

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(b) The following data was obtained in such an investigation.I .. , __(vlimA : ... .lHz V/V i

30 1.50 19.6 40 22.7 50

1.501.50 26.0

60 1.49 29.370 1.49 33.075 1.48 35.080 1.48 36.7

Add further columns for your processed data, and then plot a graph of ] IZ2 against j2on the grid opposite to test the equation.

(5). '

(c) Use your graph to detennine an experimental value for the resistance of the resistor

e ~ 9 " " . 6 ~ ' . ' * 99 . , . .. , 9 5 * 0..0 .. . "." 0 ...... ........ . ............. ...................................................................................... ......... .

(Total 16 marks)TOTAL FOR PAPER: 48 MARKS

END


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Question CYou are to ofhow the frequency of vibration in a conical flaskdepends on are then to a set ofdatafrom such an experiment.(a) (i) Blow directly into the neck of the flask listen to the sound air vibrating.Pour water into the until it is aDtJrOXlnaatel half filled and into the

What do you pitch of the vibratingwater?

(1)be a between the frequency

of the fonn

In to test this relationship she sets up following

Calibrated Loudspeakersignalgenerator

She the frequency vibratesvery loudly. Explain why of theair.

(2)

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January 2004


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(iii) Explain how she could vary, and measure, the volume of air in the flask and statea graph she could plot to test whetherf ex: vn .

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(b)

(c)

The following data were obtained in such an investigation:

324

415

the columns for your n r n , ( " p ~ data, and then plot a suitable to testopposite.

(5). 'Use your to a value for n.

ExplJin qualitatively whether your value for n is consistent with your initialations in (a)(i).

(4)(Total 16 marks)

TOTAL FOR PAPER: MARKSEND

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QC


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IYOli are to plan an d from one o ftheofhow density along thedepends on the are then to analyse aan investigation.

(a) In the the magnetic flux density is to be measured byprobe.

ofa bar magnetofdata from such

of a Hall

investigation the HaHturns wound into a solenoid(i) Prior tohad

was the

(ii) The Hall recorded at the centre ll.JiI'lHU was 67 mV themagnetic that corresponds to a ofl.OmV

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Leave ((iii) To plan the investigation of how magnetic flux densio/)B along the of theI blankbar magnet depends on the distance d from one of the poles" you may assume thatthe following apparatus is available: \.. a Hall probe with power supply .. a meter to measure output the Hall probe .. a bar magnet .. a half-metre rule

Show clearly on your diagthe sensor at the the probe with to the bar

distance d.the

.'

(iv) An initial measurement shows that at a distance of 10 mm the north pole of themagnet Hall voltage is 318 m V .Using your answer from part (ii) determine avalue the flux density at this

(8)


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Leaveb) In such an investigation it is expected that B Ikd n where k.and n are constants. Write blankthis equation in a suitable form to plot a linear graph.. . . . . . : ~ ~ H ? : ! L : / j / C ( . . . . . .

.................................. l . ~ .'::':.:.-:: .. ::'.. : ... ..................... .. .................................... .. .... The following data were obtained in such an investigation.

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5.44 20 l . C3.52 25 I2.45 301.80 351.42 401.17 44

Add your processed data to the table and then plot a suitable graph to test the above equation on the grid opposite. ..' (6)

(c) Use the gradient ofyour graph to detennine a value for 11 ... ...... .. .. ....... .. ............................ ... ... .... ......................................... ..... ..... ... ............ .. ............ ... .......................... .. .. ..................................... ............. ............ ........... ........ ... ............... ....... .. ... .... ........................... .. ........... .... .... . .......... .. ........................ ... .. ...... ... .... ... ............... -.. .... .. .. .

.................. .. .. ... .... .. .................................... ................................. .... .. ..... ....... .... ... ..... ... .. ..... (2)


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(Total 16 marks)(/ TOTAL FOR PAPER: 48 MARKSEND

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QC


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andQuestion C blank

are to plan an investigation into the between the tension in athe natural frequency ofvibration of the string in the simplest stationary waveis available:ou assume that the following

signal generatora variable a vibrator

a pulley which may be aruacrlea to the edge the bench a range suitable masses and a mass hanger

arrangement that you use to carry out

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Draw a only items listed above.

January 2005


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Leavetationary wave that may be fonned on thediagram of blank

the you would ...""..'1-". . . . . . anindication of how you would ensure that the string was vibrating at

should include forgiven tension in the string. '

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(8)


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(b) natural frequencyf of a vibrating its simplest stationary wave is blankto vary with the tension T in the string, according to an equation of the fonnf=

where k is a constant.A student investigating the. above equation obtained the following results when the mass M at the end of the string was varied.

(i) the grid opposite, plot a graph o f fagainst to test the equation. the columns provided for your processed data. .' (6)

(ii) Discuss the extent to which your graph supports the suggested equation.

(2)


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QC(Total 16 marks)

TOTAL FOR PAPER: 48 MARKSEND


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LeaveblankYou are to plan an into how the current in an a.c. circuit f lOnOI ' 1 f l " on the frequencyusing an oscilloscope as a

Question C

circuit is set up:

is to measure potential"

...... ~ , O , . . . . , ' O across the 100(i) on the diagram above where would connect the oscilloscope the With the at 0.5 V/div, followingtrace is obtained:

set at 0.1 ms/div and the voltage

(ii) Calculate the frequency of the

(iii) the voltage across 100

(iv) Calculate the peak current fo circuit.

(5)

TheI

CapacitorlOon

O----. . .JVariable

generator



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(b) The circuit on page 9 is to be used to investigate how the peak current 10 in the circuitdepends on the frequency f of the alternating current. Describe how you would carry outsuch an investigation.

(3)(c) In such an experiment the following data were obtained.

j lkHz Vo/V3.00 1.014.00 2.055.00 4.09 .6.00 5.407.00 3.50 ,8.00 2.45 -,

j

9.00 1.90 .,-'(i) Add the corresponding values of 10 to the table in the column provided.

Plot a graph of 10 againstf on the grid opposite. (4)


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(ii) If you had been doing this experiment, over what range of frequencies would you havetaken extra readings to improve your graph?............................................................................................................................................ ............................................................................. ............................................................... Estimate as accurately as possible the maximum current in the circuit.

-............................................................................................................................................ At what value of frequency does this occur?

(4)

i t- f - . - , : I - :..+ f ' l :1 I J - ' t , 1-- I + .-i.-J, I-. t! - ' . 1 ..l - . J ..

-- f' /-'- I R=Ff. -' j ' 1.. , i 'l" 1 + 'f q-:.;:1+ t ... f I ,+1 L dj: . / 4-t - H ' 1 f F-=-FIT:i i - pi -f - f---H I I j +;; _J_ - '- ; -I f!

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QC

(Total 16 marks)TOTAL FOR PAPER: 48 MARKS

END

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(b) The following data were obtained in such an investigation.

20 7063040 350

70

Use the column provided for your processed data, and then plot a suitable graph to test thesuggested relationship on the grid opposite. .' (5)(c) (i) Over what does U5f ' ; , " ,C ) l lVU appear valid') Explain youranswer.

(ii) any assumption that youo a for Ro.answer.


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(iii) Describe briefly how you would check your value Ro experimentally. I blank ., ...... y . . . . . . . . . _ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ~ ~ , 4 .... ,. .. ,. ... " ......... 5 * , " ' " . . . . ~ ~ ~ * ~ ~ ... & ~ ~ .. ~ ~ .. ..

Q1C(6)(Total 16 Iparks)

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June 2006 (Group 1)


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June 2006 (Group 2)


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January 2007


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Question CYou are to plan an investigation into the variation of the resistance of a Light DependentResistor (LOR) as the intensity of the illumination changes. A Light Emitting Diode (LED) isused to provide the illumination.

(a) On the axes below sketch the I-V characteristic for an LED. Mark an approximatescale on the voltage axis.

f

!/L. )nV/V ' (2)

(b) When an LD R is illuminated by an LED it is suggested that the resistance R of theLDR varies with the current I in the LED according to the formula

R = kI"

where k and b are constants.You are to plan to use an LED to illuminate an LD R in a controlled fashion and tomeasure the resistance of the LDR as the illumination changes. The following apparatus is available:

Light Emitting Diode Light Dependent Resistor all usual laboratory apparatus


SOLVED


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e - Leavei blankI (i) Draw the circui t you would set up to vary and record the current in the LED.II,- - - .

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(ii) Draw the circuit you w'ould set up to measure the resistance of the LDR.+ . --...,. . /-- .. '"-../ ..J- " jljl........-" ....\ / r f ), .. (( 1 ) ~ , , / : t , }I ';( -- ' J: i

(4)(c) (i) Describe how you would carry out the experiment. You should state any

precautions you would take to ens!lre an accurate outcome.

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(ii) Exp lain why a graph of In R against In J will allow you to test the relationshipbetween Rand 1. bR :: I( j..... ...... ........... .... .... .... .. ............... .. ....J .. .... .. .... ...... ... ........ ..... ................ .. .. ....... .... ...

(() R;:. Cn K} :: (11)( -I 3 t.n .J... ..... .... .... .. ....... ... ......... ..... .. .. .. .... ........ ...... ... ......... .. ...... ..... .... .. ... .... ... ... .. ..... ..... .. .... . c)' ( = I ~ : : j T LY1 ;(... .. ... ................"v'" .......;.... ....... .....!J .......... ........ ....... ......... .. ..... ..... ..... ........ .... ...ct = X ..} C (4)

(d) Such an experiment produced the following data :

JimA RID. ! "" I _ ';0.29 6550.69 234 - 0 ,3 7., ~ Vb~ - - - - - - - - - - - - - - - - - - - - 4 - - - - - - - - - - - - - ~ - - - - - - - - - -1.26 100

I2.20 52 .8I3.40 31.2I5.19 19.4I

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(6) i QC :' ~ I (Total 16 marks) i l !

TOTAL FOR PAPER: 48 MARKS

Planning Experiments QP 2

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