thermo sept15

7/25/2019 Thermo Sept15

1/12

UNIVERSITI

TLINKU

ABDUL

RAHMAN

ACADEMIC

YEAR 2OL

5

12016

SEPTEMBER EXAMINATiON

FHSC

1

024

THERMODYNAMICS

AND

ELECIBgMAGNETI$M

FzuDAY

,

18

SEPTEMBER

2015

TIME

:

2.30 PM

-

4.30 PM

(2

HOURS)

FOLJ-NDATION

IN

SCIENCE

INSTRUCTIONS

TO

CANDIDATES :

This

question paper

comprises

THREE

(3)

sections.

SECTION

A : Answer

ALL

questions.

SECTION

ts : Choose

Ol{E

(1)

question

to

answer.

SECTION C : Choose

ONE

(1) question

to answer.

NC}TES:

Please

read the instructions carefully

before

you

answer

the

questions.

For those

questions/sections

with

options, oniy the initial answers

witl

be marked.

Any

additional

answers

will

not be

considered.


2/12

2

FHSC

1

024

THERMOD\T..{AMICS

AND ELECTROMAGNETISM

Q1.

SECTION A

Answer

ALL

questions

in

this

section.

(a)

(i)

Define

heat and

temperature.

(2

marks)

(ii)

A steel

is

cooled

from

201

oF

to

102

oF.

Determine

the

change

in

the

temperature

of

the

steel

on the

Celsius scale.

(4

marks)

If an aluminum

rod

has

an initiai

length

of

2.00 cm,

find thre

rate of change

in

temperature

when the

expansion

rate is at i00

nm/s.

(3

marks)

(b)

(c)

A

perfectly

insulated

uniform

rod

has a

length

of0.650

m and

a

oross sectional

area

of

3.80

x

10-a

m2. The

temperature at one

end of the

rod

is 98.0'C. It

is

found

that the total

heat transferred

in

one

minute

is

1.70

kJ

What

is

the

temperahre

at the other end?

Given

thermal

conductivity

of the

rod is 675 Js-1m'1K-1

(5

marks)

(d)

(e)

An

incandescent

lamp fiiament

with

an

area of

50.0 mmz

operates

at 2127

'C

in a

room

with a

temperature

of

25.0

oC.

Assume

that

all

the

energy furnished

to the

bulb is radiated

from it

trf the fi.lament

acts iike a biackbody

{e

:

l),

how much

power

must be furnished

to the

bulb when operating?

(5

marks)

A

monatomic

gas

contains

478 moles

of

atoms

at

a

pressure

of

2.3f1

x

104 Pa.

It

occupies

u,roir.r*.

of

48.4 m3.

(i)

What

is the total

kinetic

energy

of the

gas

atoms?

(3

marks)

(ii)

How

many

percent

does the

root mean square

speed

(of

the

gas

atoms)

increase

if

the

pressure

is increased

to

two times of its

initial

pressure?

The

volume remains

constant.

(3

marks)

fTotal:25

marks]


3/12

3

FHSC

1 024

THERMODYNAMICS AND ELECTROMAGNETISM

Section A

(Continued)

Q2.

(a)

Three

point

charges

have equai

magnitudes,

two

being

positive

and one

negative. These charges are fixed

to

the

courers

of

an

equilateral triangle as

shown

in

Figure

1. The magnitude

of the

charges

is

3.00 pC

and

the lengths

of

the sides

of

the

triangie

are 2.AA

cm. Caiculate the

magnitude and direction

of the net force

that

charge

ts

will

experience.

(7

marks)

s

f

Figure

1

Find the equivalent

resistance for the

circuit

shown

in

Figure

2.

(2

marks)

HeRce,

determine

the current

that flows through the 10.0

CI resistor.

(4

marks)

20.0

f)

70.0

e)

t*L

(b)

(i)

(ii)

I

I

i

I

I

30.0

v---

60.0

80.0 CI

Figure 2

Define

capacitar and capacitance.

i00.0

f)

(i)

)

(2

marks)


4/12

4

FHS

C 1

024

THERMOD

IT.{AMI

C

S AND

ELECTROMA

GNETISX4

Section A

Q2.

(c).

(Continued)

(ii)

Figure

3 shows three

circuits,

each

consisting of

a switch and

two

capacitors, initialiy

charged

as indicated

(top

plate

positive).

The

switches

are

then closed. State

whether

the charges

in

the

ieft

hand

capacitor

of

each

circuit

(1), (2)

and

(3)

will inorease,

deerease

or

remain the same.

(3)

(1)

(d)

(4

marks)

(3

marks)

[Total:25

marks]

/_

J*

{_

eq

J*

-1-sq

u*

I

l-tn

os

I

*[-ut

T_T'

u'T-*T'

'cT**J*ze

(2)

Figune

3

(3 marks)

A series RCL

circuit

contains

a 3.80

pF

capacitor

and a

generator

rvhose rms

voltage is

11.0

V.

At a

resonant

ftequency

of

1.20 kHz, the

power

delivered

to

the circuit

is 30.0

W. Find the

vai,ue of

:

(i)

(ii)

the

inductance,

the resistance.


5/12

5

FHS

C

1

024 THERMOpIT{AMTCS

ANp

ELECTROMAGNETIISnA

SECTION

B

Answer

any one

question

in this section,

Ql.

(a)

Figure 4

shows

the

design of

a

iiquid-in-glass therrnometer

which is

commonlv found

in

science

laboratorv.

Bulb Thread

Thin capiliarv

Figure

4

Glass

stem

(i)

Give

TWO

(2)

reasons

why

mercury

is

normaliy

used

as the

liquid

in

this tipe

of

thermometer.

(4

marks)

(ii)

Suggest

TWO

(2)

possible

ways

to

increase

the

sensitivity

of

the

thermometer. JustifV

vour

answers.

(4

marks)

Your friend

thinks that Zeroth

Law of

Thermodynamies is related to the

design or

working of this iiquid-in-glass

thennometer but

he

ean't

quite

figwe

out.

(iii)

State Zeroth Law of

Thermodynamies

(2

marks)

(iv)

Expiain

how

Zeroth

Law of

Themnodynamies

is

reiated

tc

the design

or

working

of

the thermorneter

(2

rnarks)

Given

that

the bulb

of the themrometer

has a volurne

of

0.500 m1, and the

diameter

and length of

the thin capiliary

are

0.250 mm

and

30.0

om

respectively.

An

unknown

liquid Z

with thermal

volume expansion coeffi.cient,

p

af

2.45

x

10-+ K.

1

is

used

to fiil

up

the butb

at

-10.0

oC.

(v)

Identify

the sensitivity of

the thermometer in the units

of

oC/mm.

(4

marks)

(vi)

Determine

the

range

of

weirking temperature suitabie for

this

thermometer.

(3

marks)


6/12

6

FI{SC1O24

TI{ERMODYNAMICS AND

ELECTR

ETISM

Section B

O1.

(Continued)

(b) (i)

Expiain why the

sensation of cooiness experienced

differs when

our

bar e

foot

steps

on a

tiie

floor

and

a

carpet that

have the same

temperature,

separately.

(2

marks)

When a

100

ml

aiuminium

container of

mass

85.0

g

at temperature

20.0

C

is

fuily filled

by

water of 85.0

oC,

the

equiiibrium

temperature

of both

the iiquid

and

container

is

68.0

oC.

Compute

tire

amount of

energy

loss

to the

surrounding

and

suggest

one meehanism of

the

energy loss.

(4

marks)

fTotal

: 25 marks]

(ii)

(a)

Q2.

A vessel

contains 0.100

kg

ofheiium

gas

at a

pressure

of

i50

speed of the helium atoms

is 1.35 km/s. Determine:

(i)

the volume of the

gas,

(ii)

the

temperature

of the

gas.

(Molar

atomic

mass

of helium is 4.00

g/mol)

kPa

The

rms

(5

marks)

(4

marks)

(b)

(i)

Write

an equation which represents

the First

Law

of

Thermodyramics,

by defining the

syp$e1s used..

(2

marks)

(ii)

An

ideal

gas

undergoes the

process

qbca

showt

in

Figure 5. The heat

gained

in

the

process

ab

is 546

J,

whiie in

the

process

bc,

tbe system

loses 62.0 J.

In

the

process

ab,the

system

performs

310

J of

work,

while in

process

ca,

work

is done on

the

system

in the amount of 233

J.

How much heat is

gained

by the system in the

process

ca?

(8

marks)

Figure

5


7/12

7

FHSC1 024

THERMODYNAMICS

AND

ELECTROMAGNETISM

Section

B

02.

(Continued)

(c)

A refrigerator has

a

COP of 2,10. In each cycle,

it

absorbs

3.40

x

104

J of

heat

from the cold reservoir.

(t

How

much mechanical energy is required for each cycie

to

operate the

refrigerator?

During each

cycle, how much heat,

Q,n

,

temperature

res

ervo

ir?

(3

marks)

is

discarded

to

the

high-

(3

marks)

fTotai:25

marks]


8/12

8

FHSC

1 024 THERMODYNAMIC S

AND EI-ECTROMAGNETISM

Qi.

(a)

SECTION C

Answer

any one

question

in

this

section.

By

using

Kirchhoff

s

Laws, determine

the current

labelled

the circuit

given

in Figure

6.

of

the circle.

(ii)

Find the

eiectric

potential

at the centre

of the sircle.

in

each

branch

of

(7 marks)

7.C10 CI

3-00

t)

13.0V

4,S0a

Figure

6

Qr

--G-*

Qs

Figure

7

Figure 7 shows

four

point

charges

labelled

by

Qt

:

+15,0

nC,

Qz

=

*15.0

nC,

Q,

:

+15.0

nC

md

Qa

:

-15.0 nC.

These charges

are

placed

on

the

circumference of

a

circle

with a

radius of

40.0 cm.

(i)

Find the electric

fieid

strength

(magnitude

and direetion)

at

the

centre

T^

(b)

I

Qz*

t

t

?Qo

I

(4

marks)

(3

marks)


9/12

9

FHSC 1 024

THER.MODYNAMICS

AND

ELECTROMAGNETISM

Section C

Q1.

(Continued)

(A)

the equivalence

resistors of the

circuits,

(B)

the equivalence

capacitance

of the

circuits,

(C)

the

electric

eharges

in

5.00 pF capacitor.

(c)

S.00

ilfl

2.00

f)

;)

Switch

Figure

I

(i)

Refer

to

Figure

8,

assurning

batteries

have constant

DC

power

suppil',

determine:

(2

marks)

(2

marks)

(3 marks)

(ii)

The switch

in Figure

8

is

connected

to resistors

after the

capacitors are

firlly charged.

Determine

the time

required

when the

charge,

Q

i,n

capacitors

have dropped

to 0.0600

pC.

(4

marks)

[Total:25

marks]

5.80

Q


10/12

10

FHSC I 024 THERMODYT\AMr C S

ANp ELECTROMAGNETISII

Section

C

(Continued)

Q2.

(a)

Four

particles

pass

through

a square

region

of uniforrn

magnetie

field

shoqm

in

Figure

9. The

magnetic

field

inside the square region is

perpendicular

to

the

page,

and

tire

field outside

the

region is zero. The

paths

followed

by

particies

I

and 2

are

shown;

while for

particles

3

and

4

the direstion

of

their

velocities

and

the

points

at

which

they enter the

region

are

shown.

The

paths

of

all

particles

iie in the

plane

of the

paper.

Given

particle

3 has a

mass

of

ru, a speed

of

v, and a charge

of

-q

while

particle

4

has

a

mass 2m,

a

speed

2v, and

no

charge.

Figure

I

Particle

t

has

a

mass

2m, a

speed

2v,

and a

positive

eharge

+2q.

Frnd

the direction

of

the uniform

magnetic

field

in

the

square

region

and

state

the rule

used to determine

the answer.

(2

marks)

Assume

that

the only

force

acting

on

the

partieies as

they move

through the

rnagnetic field

is the field

force. What

happen

to

particle

1's

kinetic

energy

as

it

moves

through the field?

Give

your

reason.

(2

marks)

Which

particle

feeis

the largest

magnitude of force

as it

passes

through

the

field?

Give

your

reason.

(3

marks)

(0

(ii)

(iii)


11/12

11

F'HS C

1 024 THERMOD\TNAMIC

S AND

ELECTROMAGNETISM

Section C

02.

(Continued)

(b)

Suppose

that the

length of the

moving rod

in Figure

10 below

is

/

:

0.500

m,

the magnetic

field

strength

is

,B

:

1.00

T directed

into the

page

while its

speed

is

v:

0.250

m

s-1

and

the resistance

of

the

circuit

is,R

=

0.0500

A.

magnene

ftcld

inta

page

t

r3

\:v

a

(?t

t'>,

'{:r

Figure

1,0

What is

the emf

generated

around the

circuit?

Find the curreRt

flows

around

the circuit

and its

direetion.

(i)

(ii)

(iii)

(3

marks)

(4

marks)

(c)

What

is the direction

of

the force acting

on

the

moving rod

due

to the

factthat

a current

is

flowing

along

it?

(1

mark)

A

plane

circuiar

loop of

conducting

wire

of radius

r

:

2A.A

cm which

possesses

N

=

10.0 turns

is

piaced

in a uniform

magnetic

fieid.

The

direction

of

the

magnetic

field makes

an

angle

of 30.0

with

respeet

to the

normal

direction

to

tire loop. In

a time interval

of

Ar

=

20.0

s,

the

magnetic

fietd

strength.B

is increased

at a constant

rate from

81= 2.00

T

to

Bz

=

8.00 T.

(i)

What

is

the emf

generated

around

the ioop?

(7

marks)

(ii)

If

the electrical

resistance

of the ioop

is R

=

2.00

O, what ourrent

flows

around

the loop

as the

magnetic

f,reld

is increased?

(3

marks)

[Total:25

marks]

&a

t8l

lS

aa

aa

&a


12/12

12

FHS C 1 O

24 THERMO

D

\T.{AMI

C

S AND

ELE C

TROMAGNETI SM_

List

of

phvsicul

constants:

Acceleration of

gravity,

g

=

9.80

m s-2

Avogadro's

number,

N,q

=

6.02x

1023 mol-l

Atmospheric

pressure,

P*,=l alTn

=

i.013

x

10'

Nm

Boltzmann's

constant,

ft

=

1.38

x

10-23

.T K-1

Stefan-Boltzmann

constant,

o

=5.67

x10-8

Wm-2'K4

Penneability

of free

space,

V

=

4nxIA-7

T

' mA-'

Pennittivity

of free

space.

e :

8.85x10-12

C2Nr

' #

Universal

gas

constant,

ft

=

8.314

J mol-i

K-1

Coulomb's

constant, k

=8.99

x

l0eNm2C-2

Coefficient

of thermai

expansion

for

platinum,

apt'm*=9.00xi0{

uC-i

Coeffrcient

of

thermal expansion

for copper,

&,opp ,

=

16.0x10{

oC-l

Coefficient

of

thermal

expansion

for aiuminum,

a,opp,,

=

23.0x10{

oC-]

Specific

heat

capacity of

water,

c*o, ,

--

4186 Jkg

/

C

Specific

heatcapaeity

of

aiumifrw,

cot,^inu,

=9A2Jkg/ C

1

nutritional

Calorie

(Cal)

=

1000 cal =

4186 J

Electron

volt,

1 eV

=

1.60

x10-1e

J

Charge of electron

,

e

=\.60

x

10-1e

C

Mass of

electron,

m,

=9.11x10-31

kg

Mass ofprotoin,

mo=1.67x10t7

kg

Mass

of

neutron, m,

=L.67

x10-27

kg

thermo sept15

Documents