# WAEC Physics Practical Answer – May/June 2017 Expo

100% Correct WAEC Physics Practical Answer Solution – May/June 2017 Expo Runs

**Physics Practical Solution**

2)

2b)

bi)The boiling point of a liquid is the temperature

at which the vapor pressure of the

liquid equals the pressure surrounding the liquid

and the

liquid changes into a vapor.

bii) impurities increases the temperature range a

substance can exist as a liquid

========================

(1)

TABULATE:

i:1,2,3,4,5,

L(cm):80.00,70.00,60.00,50.00,40.00

t1(s):17.87,16.22,16.09,14.08,13.28

t2(2):17.56,16.46,15.09,14.77,13.36

t(s)mean:17.715,16.340,15.590,14.425,13.320

T(t/10)s:1.7715,1.6340,1.5590,1.4425,1.3320

LogT(s):0.2483,0.2133,0.1928,0.1591,0.1212

Log L(cm):1.9031,1.8451,1.7782,1.6990,1.6021

Log T*10^-2(s):24.83,21.33,19.28,15.91,12.12

Log L*10^-1(cm):19.031,18.451,17.782,16.990,16.021

SLOPE(s)=(LogT2*10^-2 – LogT1*10^-2)(/Log L2 *10^-1 – LogL1*10^-1)

=(21.33-12.12(s))*10^-2/(18.50-16.02(cm)*10^-1)

=3.714*10^-1

=0.3714cm^-1

1axi)

i)ensured supports of pendula were rigged

ii)avoided parallax error on meter rule/stop watch

1bi)

simple harmonic motion is the motion of a body whose acceleration is always direct towards a fixed point and is proportional to the displacement from the fixed points

1bii)

T=1.2secs

Log 1.2=0.079

0079 shown on graph with corresponding Log L read L correctly determined

===========================

NO 3 GRAPH

(3a)

TABULATE:

x(cm):10,20,30,40,50,60

V(v):0.65,0.75,1.00,1.20,1.45,1.55

I(A):0.20,0.30,0.35,0.40,0.45,0.55

LogV(v):-0.187,-0.125,0.000,0.079,0.161,0.190

LogI(ohm):-0.699,-0.523,-0.456,-0.396,-0.391,-0.360

SLOPE(s):=( LogI2-LOgI1)/(LogV2-LogV1)

=-0.2-(-0.7)/0.3-(-0.2)

=0.5/0.5

=1AV^-1

3axi)

i)ensured clean/tight terminals

ii)open key when reading was taken

3bi)As × increases the Brightness of the bulb increases, voltage and current through the bulb increases hence brightness increases.

3bii)Electrical device that do not obey ohm’s law are..:

¡)Diode

¡¡) capacitor

¡¡¡)transistor

¡v)thermistor

V)thyristor

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**GOODLUCK!!!**

*1(a).*

You are provided with two retort stands, two metre rules, pieces

of thread and other nec es s ary apparatus.

(i). Set— up the apparatus as illustrated above ensuring that the

strings are permanently 10 cm ﬁom either end of the rule.

(ii). Measure and record the length L = 80 cm of the two strings.

(iii). Hold both ends of the rule and dis place the rule slightly, then

release so that it oscillates about a vertical aXis through its

centre.

(iv). Determine and record the time t for 10 complete os cillations.

(v). Determine the period T of os cillations.

(vi). Evaluate log T and log L. Solutionwap.net

(vii). Repeat the procedure for four other values of L = 70, 60, 50

and 40 cm.

(viii). Tabulate your readings.

(ix). Plot a graph with log T on the vertical aXis and log L on the

horizontal aXis.

(X). Determine the slope, s, and the intercept, c on the vertical aXis.

(X). State two precautions taken to ensure accurate results.

[21 marks]

*(b).*

(1). Deﬁne simple harmonic motion [2 marks]

(ii). Determine the value of L corresponding to T = 128 ﬁpm the

graph in (a) above.

[2 marks]

*2(a).*

You are provided with a beaker, a thermometer, a stirrer, stop

watch/clock, measuring cylinder, table salt, water and other

nec es s ary materials .

(i). Measure 200 cm3 of water into the beaker.

4

(ii). Heat the water until it boils steadily for about 2 minutes.

(iii). Read and record the boiling point b0.

(iv). Add table salt of mass M = 10.0 g to the boiling water and

stir continuously until another boiling point b1 is attained

(v). Read and record b1

(vi). Evaluate 6 = (br- ho).

(vii). Using the same mixture, repeat the procedure four more

times by adding 10.0 g of salt each time to give the cumulative

mass Mjofsalt as 20 g,30 g,40gand50 g.

(viii). In each case allow the mixture to boil steadily for at least 2

minutes then read and record the boiling point bi.

(ix). Tabulate your readings.

(x). Plot a graph with M- on the vertical axis and 0 on the

horizontalaxis.

(xi). Determine the slope, s, of the graph.

(xii). State two precautions taken to ensure accurate results.

[21 marks]

*(b).*

(i). Deﬁne the boiling point of a liquid. [2 marks]

(ii). What effect does impurities have on the boiling point of a

liquid? [2 marks]

*3a)*

You are provided with cells, a potentiometer, an ammeter, a

voltmeter, a bulb, a key, a jockey and other nec es s ary materials.

(i). Measure and record the emf E of the battery.

(ii). Set— up a circuit as shown in the diagram above.

(iii). Close the key K and use jockey to make a ﬁrm contact at]

on the potentiometerwire such such that P] = x = 10 cm

(iv). Take and record the voltmeter reading and the

corresponding ammeter reading .

(v). Evaluate log V and log I

(vi). Repeat the procedure for other values of x = 20, 30, 40, 50

and 60cm.

(vii). Tabulate your readings.

(viii). Plot a graph with log I on the vertical axis and log V on the

horizontal axis.

(ix). Determine the slope, s, of the graph.

(x). Determine the intercept, c, on the vertical axis.

(xi). State two precautions taken to ensure accurate results.

[2 1marks ]

*(b).*

(i). Howis the brightness of the bulb affected as x increases?

Give a reas on for your answer. [2 marks]

(ii). List two electrical devices whose actions do not obey Ohm’s

law. [2 marks]

*ANSWERS?? TO THE QUESTIONS ABOVE*??

*1.*

This experiment involves Biﬁlar suspensions the motion of

which should be like when opening a tap.

In part (a) candidates are expected to:

– Measure and record ﬁve values of L to at least 1 d.p. and in

trend. Trend: As L increases, t decreases

– Evaluate ﬁve values each of T, log L and log Ito at least 3 s.f.

– Record data in composite table. Solutionwap.net

– Plot ﬁve point, correctly using reasonable scales and

distinguished axes.

– Draw line of best ﬁt.

– Determine the intercept on the vertical axes and the slope of the

graph us ing large right- angled triangle.

– State any two of the following precautions in acceptable

language.

– Ens ured supports of pendula were rigged.

– Avoided parallax error on meter rule/ stop watch.

– Zero errorwas noted and corrected on metre rule/ stop

watch/ clock

– Ens ured smooth and regular os cillations in a horizontal plane.

– Repeated readings shown on table.

Part (b) expected answers are:

Simple harmonic motion is the motion of a body whos e

acceleration is always directed towards a ﬁxed point and is

proportional to the displacement ﬁom the ﬁxed point.

T = 1.2 secs

Log 1.2 = 0.079

0.079 shown on graph with corresponding log L read

L correctly determined.

*2.*

The aim of this experiment is to investigate the effect of

dis 3 olved s alt (impurity) on boiling point of water.

The expected answers are:

Value of hi read and recorded in °C.

Five values of hi read and recorded in °C to 1d.p and in trend.

(Trend: As M increas es, bi increas es)

Five values of M correctly recorded in gram.

Five values of 6 = (bi – b0) correctly evaluated to 1d.p.

Composite table showing bo,bi,1V[j, and 6.

Candidates are also expected to:

— Plot ﬁve points on graph.

– – Distinguish between the axes.

– – Choos e reas onable s cales.

— Draw line of best ﬁt.

— Determine the slope of the graph.

— State any two of the following precaution in acceptable

language.

– – Avoided splas hing of water.

– – Avoided parallax error on thermometer/ stopwatch/ clock

– – Avoided noted zero error on stop watch/ clock

– – Ens ured thermometer did not touch the beaker.

– – Repeated readings shown on the table.

— No drop of wateris allowed to escape after weighing.

– – Thermometer not allowed to rest on the has e of beaker.

– – Stirred after adding 3 alt to ensure dis 3 olution.

(b).

(i). This is the temperature of a liquid at which the saturated

vapour pres sure of the liquid equals the extemal atmospheric

pres s ure.

Impurities increase the boiling point of a liquid.

NB: The graph should looklike the one below.

*3.*

In part (a) candidates were required among other things, to:

– Measure and record the emf of the battery involts to at least 1

d.p.

– Read and record sixvalues of, V and Ito at least 1 d.p and in

trend. (Trend as increases, V and I also increases)

-Evaluate sixvalues of log Iand log Vto at least 3 d.p.

– Record V, I, log V and log I in composite table.

– Plot six points correctly using reas onable s cale.

– Drawline of best ﬁt on distinguished axes.

– Determine the slope of the graph using large right angled

triangle and recording of the intercept on the vertical axis.

State any two precautions in acceptable language

– Ens ured clean/ tight terminals.

– Open key when reading was not taken.

– Avoided parallax error in ammeter/ voltmeter.

– Avoided sliding of jockey on the potentiometer wire.

b(i).

– Brightnes s of the bulb increas es.

-Voltage/ current through the bulb increas es.

(ii). Devices that do not obey Ohm’s law.

Diode

Trans is tor

Thyris tor

Capacitor

Therrnis tor

The graphs are wrong oh……for the number 2 it must pass through the origin