51635094 2nd Physics Short Ans MCQ

8/12/2019 51635094 2nd Physics Short Ans MCQ

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SOLUTION OF BOOK QUESTIONS 2nd YEAR PHYSICS

CHAPTER # 12Q#1

The potential is constant throughout a given region of space .isthe electric field is zero or non zero in this region?

Ans#1:Electric field E and potential difference are related by equation,

E =- v/ rWhen the potential is taken as constant which means v= constant then the

potential difference becomes zero v=so, E =/r ! E = This relation tells that electric field is zero in a region of where the

potential is constantQ#":

uppose that $ou follo% an electric field line due to a positivepoint charge .do electric field and the potential increases or decreases?Ans#":

elation for the electric field and and electric potential are

E= 1/&' (!) */r" and v=1/&' (!) */ rthis gives for same charge

E+1/r" ,+ 1/rWhen we follow electric field line due to positive charge, distance from

positive charge increases which cases to decrease electric field and

potential"

Q#-:o% can $ou identif$ that %hich plate of a capacitor is positivel$

charged?Ans#-:

When a freely suspende#d positively charged gold leaf of

electroscope is $brought near to one of the plates of capacitor the

divergence to gold leaf shows that the plate of the capacitor is positivelycharge d otherwise negatively charged""

Q#&:

Prepared By:

Asif Rasheed BS(Hons) PhysicsContact# 0344-74!3"403$3-7!"00$!

%


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escri0e the force or forces on a positive point charge %henplaced 0et%een parallel plates

&a' 2ith si3ilar and e*ual charges.405 2ith opposite and e*ual charges.

Ans#&:The electric force ( on a charge q due to eclectic field E is given by

6= *E&)' When a positive point charge is placed between parallel plates with

similar and equal charges" it will e*perience no electric force because

electric field between the plate is zero . 6=*E

6=*45 = !6=&+' When a positive pint charge is placed between the plates of the

capacitor it will e*perience electric force , 6=*E

ue to electric field set up from positive to negative "

Q#7:

Electric lines of forces never cross each other. 2h$?Ans#7:.o, two electric lines of forces never cross each other because /E0

only one direction at a given point "if two lines cross each other then there

will be more directions at a point which is impossible"Q#8:

9f appoint charge * of 3ass 3 is released in a non unifor3electric field %ith field lines pointing in the sa3e direction %ill it 3aea rectilinear 3otion?Ans#8:

1otion along a straight line is called rectilinear motion when acharge /q0 of mass /m0 is released in a non uniform electric field" 2t will

not move in a straight line and adopts irregular path due to variable electric

field"

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Q#;:9s E necessaril$ zero inside a charged ru00er 0alloon if 0alloon is

spherical? Assu3e that charge is distri0uted unifor3l$ over thesurface ?Ans#;: 4es E is necessarily zero inside a charged rubber balloon if balloonis spherical and enclosed no charge but chage is distributed uniformly over

its surface" )ccording to 5auss6s law"


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Electrons tend to go to a region of high potential because high

potential is more positive than the lower potential as the charge on electron

is negative"

CHAPTER # 13QBET9CD AD AD2E:Q#1: A potential difference is applied across the ends of a copper %ire.%hat is the effect of drift velocit$415 9ncreasing the potential difference.4"5 decreasing the length and the te3perature of the %ire.Ans#1 The uniform velocity that the free electrons acqure opposite to the

electric field of battery is called the drift velocity"&%' the increase of potential difference makes the electric field strong

which cases to increase the drift velocity

&3' the decrease in length an temperature of the wire which causes to to

increase the drift velocity of the free electron in the wire"

Q#":o 0ends in %ire effects it@s electrical resistance?

Ans#-We know that =; l


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increases"

Q7#:2hat are the difficulties in testing %hether the fila3ent of

lighting 0ul0 o0e$s oh3 la%?Ans#7

)t the beginning, when bulb is turned ?. its filament is at low low

temrature and it obeys ?hm6s law" 2 @ A

ater on when current rises to its ma*imum value "the ma*imum power

8=23 dissipated across the filament which increases resistance but current

increases at lower rate and does not obey ohm6s law

Q#8:9s the fila3ent resistance lo%er or higher in a 72 "", light

0ul0 than in 12 "", 0ul0?Ans#8

esistance of %stbulb= %=Besistance of 3ndbulb =3=B

8ower of first bulb =8%=C!! watts

8ower of 3ndbulb=83=%!! watts

Aoltage =A=33! volts

+y applying the formula, 8=A3!!$>F

Q#;:escri0e a circuit %hich %ill giva a continuousl$ var$ing

potential?

Ans#;8otentiometer is an instrument which gives continuously varying

potential" 2ts circuit diagram is given as" When the sliding contact G is

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C


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moved from ) to + r

varies from ? to and potential varies from ? to E the current following

through is given 0$ F 9=E/ GGGG15The potential drops across

HrI is given 0$ ,=9r as 9=E/ so,=E/ )r ,= r/ E GGGGGG"5This gives us continuously varying potentialQ#>:

E)plain %h$ the ter3inal potential difference of a 0atter$decreases %hen a current dra%n fro3 it is increased?Ans#>

The terminal potential difference is given by " Gonnected in the formofmesh )+G) " a battery of emf E is connected between points ) and G

through a switch "a sensitive galvanometer is of resistance g is

connected between points + and "

2ts equation is , 1/"= -/& GGG.15

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eter3ination of unno%n resistance:To determine unknown resistance in the arm containing >&>=*Then known value of %, 3" )nd :are so adHusted that galvanometer no

deflection "then from equation no i%


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+ = K! &.


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uppose that a charge * is 3oving in a unifor3 3agnetic field%ith a velocit$ v. 2h$ is there no %or done 0$ the 3agnetic force thatacts on the charge *?Ans#8:

) charge q is moving in uniform magnetic field +, with a velocity A

in a

Gircular path due to magnetic force" The angle between

magnetic force and velocity will be D!!"work done is given by ,

W = ("d = (d cos D!! =! &as cos of D!! is zero'"

o work is being done "

NOL

9f a charged particle 3oves in a straight line through so3eregion of space can $ou sa$ that the 3agnetic field in the region iszero?Ans#;:

.o, when a particle moves in straight line in the direction of

magnetic field" M

" q o v

The force acting on charge will be zero as angle is ! ! charge q and

magnetic field is parallel so,(= qv+sin!!= qv+&!' = !

Therefore we can not say magnetic field in this zero"

NO$

2h$ does the picture on T, screen 0eco3e distorted %hen a3agnet is 0rought near the screen?)nsOJ$

)s the picture is formed on the TA screen due to the electrons , when

a magnetic is brought is near the TA screen ,the beam of electron is

deflected due the magnetic force which is given by, (= ev+sinP! "on the

each electron"

Q#9s it possi0le to orient a current loop in a unifor3 3agnetic field

cush that the loop %ill tend to rotate? E)plain.

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D

D!o

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Ans#The torque acting on a current carrying loop in the uniform magnetic

field is given by,

Q&torque '=.2)+cos@ ,Where @ is the angle between + and plane of

loop "if @= D!! then cos of D!!= ! so torque will be zero here this shows that

if plane of loop is oreintted at D!!with + "Then loop will not tend to rotate"

Q#1o% can a current loop 0e used to deter3ine the presence of a

3agnetic field in a given region of space?Ans#1:

When current carrying loop is placed in the presence of a magnetic

field with its plane makes an angle @ with + "The torque acting on it will be

Q&torque '=.2+)cos@ if current loop deflects , filed is present other wise

not"

Q#11o% can $ou use a 3agnetic field to separate isotopes of

che3ical ele3ent?Ans#11:

When isotopes of chemical element are proHected in a magnetic field

at right angle" then magnetic force ,

(b= ev+sinD! = ev+

8rovide centripetal force , (c = mv3


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&a' when plane of the coil is oriented parallel to to + "then

+= and cos = 1 so N4tor*ue 5=D9MA415 = D9AM43a)5 +=and cos = N4tor*ue 5=D9MA45 =at this the torque will be minimum"

Torque will be ma*imum

&b' when plane of coil is oriented at right angle to + then angle will be D!

so,

Q#1-A loop of %ire is suspended 0et%een the poles of a 3agnet %ith

its plane parallel to the pole faces. 2hat happens if a direct current uisput through the coil? 2hat happens if an alternating current is usedinstead?Ans#1-J

Torque on loop wire is given by , Q&torque '=2+)cos+

When the loop of wire is suspended between the poles of a magnet with itsplan parallel to pole faces then + = and cos = then we get theresult

N4tor*ue 5=9MAcos =if direct current or alternating current is passed through the coil "these

current have no effect on the loop

Q#1&2h$ the resistance of an a33eter should 0e ver$ lo%?

Ans#1&:)mmeter is always connected in series the magnitude of current

decreases through through the circuit with the presence of ammeter "to

measure

9 ma*imum current the resistance of ammeter should be very small as

compared to the resistance of circuit"

Ans#17:2h$ the volt3eter should have a ver$ high resistance?

Ans#17:Aoltmeter is always connected 2 in parallel with two points where

potential is to be measured" the potential across the points decreases with

presences of voltmeter because it draws some current 2v of the circuit " to

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reduce the current through voltmeter ,the resistance of voltmeter should be

large as compared to the resistance of circuit "

) 9 M

CHAPTER # 15

Q#1oes the induced e3f in a circuit depend upon the resistance of thecircuit?oes the induced e3f depends upon the resistance of the circuit ?Ans#)ccording to (aradays law "emf is given by

(=-. RI


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Q#-A light 3etallic ring is released fro3 a0ove into a vertical 0ar 3agnet.,ie%ed for a0ove does the current flo% cloc%ise or anticloc%ise inthe ring?Ans#-)ccording to lens6s law the direction of induced current will oppose the

motion of ring towards the bar magnet "for this purpose, the induced current

should flow in the clock wise direction the ring"

Q#&2hat is the direction of the current through resistor in fig.? %hens%itch is

4a5 closed405 opened

Ans#&

a5 )s the switch is closed, according to lens6s law, the direction ofcurrent induced in will be in anti clockwise direction"

05 ) switch is opened according to lens6s law the direction of current

induced in will be in the clock wise direction

Q#7oes the induced e3f al%a$s act to decrease the 3agnetic flu) througha circuit?Ans#7

.o, induced emf does not always act to decrease the magnetic flu* through

the circuit "according to lens6s law ,when bar magnet with . pole is moved

towards a loop flu* decreases and when it taken away from a loop flu*

increases which case emf induced"

Q#82hen the s%itch in the circuit is closed a current is esta0lished in thecoil and the 3etal ring Lu3ps up%ard 4fig.5 %h$?escri0e %hat %ould happen to the ring if the 0atter$ polarit$ %erereversed?Ans#8When switch is closed, the changing flu* of coil causes to induce current

in the metal ring which produces flu* opposite to that of coil and ring isreplaced and Humps upward" ame thing will be happen if polarity of the

battery is reversed"

Q#;

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%:


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The fig. sho%s a coil of %ire in the )$ plane %ith a 3agnetic fielddirected along the $ J a)is.Around %hich of the three coordinate a)es the coil should 0e rotated inorder to generate an e3f and a current in the coil?Ans#;The coil must be rotated about about *-a*is to get change of magnetic flu*

and an induced current through it"The emf induced in the coil is given by

(=.w)+sinP!"only in this case emf is induced"

2f the coil rotated about z-a*is then no change of magnetic flu* takes place "

2f coil rotated through y-a*is then the flu* through it will be zero"bo% %ould $ou position a flat loop of %ire in a changing 3agnetic field

so that there is no e3f induced in the loop?Ans#>2nduced emf is given by ,

(=.w)+sinP!.=% so,(=w)+sinP!

)s flate loop of wire is parallel to changing magnetic field then P=!!

(=w)+sin!! = ! this shows that nom flu* change through it and hence noemf is induced"

Q#9n a certain region the earth@s 3agnetic field verticall$ do%n .%hen aplane files due to north %hich %ingtip is positivel$ charged?Ans#The magnetic force on a moving electric charge is given by ,

( = -e &A S +'"

this relation shows that ( acting at right angle to v is towards north + is

vertically downward ,the electron moves towards left

. direction of ( is directed towards west "

w E Q#1ho% that (and


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Ans#1(= W


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%' The magnetic field must be applied by permanent magnet and

not by electromagnet"

3' )n arrangement to rotate the coil armature should be

provided"

Q#1-9s it possi0le to change 0oth area of the loop and the 3agnetic fieldpassing through the field and still not have an induced e3f in the loop?Ans#1-4es, it it is possible in the magnetic flu* takes due to the change in the area

of the loop and magnetic field, no emf will be induced in the loop"

1agnetic field is given by "

RI = + " ) =+RcosP

if the vector area R) is parallel to magnetic field +"

P = !! so,

RI =+R)cos!! cos!=%RI =+R)

if b + and ) are constant then , RI =!

U =-.RI


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Eddy currents oppose the cause which produces it" Therefore ,the

oscillations of magnet are strongly damped"

Q#186our un3ared %ires e3erge fro3 a transfor3er. 2hat steps %ould$ou tae to deter3ine the turn@s ratio?Ans#18(our wires coming out of transformer are the ends of two coils &pXs' of

transformer "each coil has negligible resistance for "G "the coils are

separated as primary and secondary" an alternating voltage of known value

vpto the primary coil the output voltage across the secondary coil" The turn

ratio of the coil is determined as,

As


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%&'SS PAP'RS R $*+ ,'AR PH,SCS

8942G G9#%3Q#1: Electric lines of forces never cross each other. 2h$?Q#": o electrons tend to go to region of high potential or of lo%potential?Q#-: 9s E necessaril$ zero inside a charged ru00er 0alloon if 0alloon isspherical? Assu3e that charge is distri0uted unifor3l$ over thesurface?Q#&: o% can $ou identif$ that %hich plate of a capacitor is positivel$

charged?

8942G G9 # %:%' 2f last band is not silver not gold then tolerance------

a' ! b' %! c5 "O d' :!3' ) comple* system consisting of number of resistor is solved by ----

a' oule6s law b' ?hm6s law c' coulomb6s law d5 Pirchhoff s la%:' in metals the current flow due to the motion of M

a5electron b' proton c' holes d' both a and b>' the unit of electromotive force is ------

a' b' G c' . d5 ,C' The colour code usually consist of ---------

a' 2nfinite band b' 3 band c' : band d5 & 0and' uring the electrolysis process, density of Gu?>-----

a' 2ncreases b' decreases c5 re3ains constant d' non of theseL' The liquid which conduct electricity is called, ------

a' 2nsulator b' conductor c5 electrol$te d' both aXb$' The drift velocity of electrons is

a' %!:m


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%!' (our similar wires of each resistance 3!F attached to form squre then the

resistance between two corners is-----

d' a' !F b' %!F c5 "R d' >!F%%' Why the resistor add in series ---

a' ivide the voltage b' increase the the voltage c5 decrease the voltage d'non

%3' 2f a >! watt light bulb burns for 3hours, how much heat is generatedY

a' :$$*%!: 05 ">>S1- c' ! d' D!

Q#1:o 0ends in %ire effects it@s electrical resistance?

Q#": 2h$ does the resistance of a conductor rise %ith te3perature?

Q#-:2hat is the %heat stone 0ridge? o% can it 0e used to deter3ine anunno%n resistance?Q#&:

escri0e a circuit %hich %ill giva a continuousl$ var$ing potential?

8942G G9 #%>%' The unit of magnetic flu* is----------

a' Weber mZ3 b' Weber m-3c' Tesla d5 2e0er3' ) galvanometer is converted into an ammeter by connecting a

suitable-------

a5 Uo% resistanceb' high resistance c' comparing voltage d' non ofthese

:' The magnetic induction is also called -----

a5 6lu) densit$ b' magnetic intensity c' flu* d' electric intensity>' Which of the following is scalar quantity ------

a' emf b' flu* density c' magnetic flu* d5 a cC' The working of a galvanometer depends upon

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%D


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2h$ the volt3eter should have a ver$ high resistance?Q#7:

o% can $ou use a 3agnetic field to separate isotopes of che3icalele3ent?

Q#8:9f a charged particle 3oves in a straight line through so3e region ofspace can $ou sa$ that the 3agnetic field in the region is zero?

8942G Gh#%CTick the correct answer

%' The fact that eclectic current produces magnetic field was discovered

by[[[[

a' 1ichel faraday 05 ens arrestedc' 9enry d' )mperes3' The current produced due to the phenomena of electromagnetic

induction is called[[[

a' 8ositive current b' .egative current c' Gonventional current d59nduced current

:' ens law deals with the[[

a' 1agnetic field of emf b' irection of emf c5 irection ofinducedcurrent d' )ll

>' The 2 unit of mutual induction is[[

a5 ,sec/Ab' A)


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then motional emf is[[

a' "G generator 05 .K Votor c' )"G 5enerator d' )ll of these%!' The magnet falls with its -pole along the a*is of a ring the

current generator is

[[[[[ and acceleration is[[[[

a' Glock wise, \g b' Kloc %ise Wg c' )nti clock wise, \g ')nti clock

Wise, ]g

%%' Which of the following remains constant in a

transformer[[[B

a' Kurrent b' Aoltage c' 8ower d' (requency%3' 2n an open ring magnets are falling along the a*is of the ring,

The current generated has direction[[[[

a' Glock Wise b' )nti clock wise c5Xerpendicular to 3agnetd' ^ero

Q#1: Kan a .K 3otor 0e turned into a .K generator? 2hat changesare e*uired to 0e done?Q#": oes the induced e3f al%a$s act to decrease the 3agnetic flu)

Through a circuit?Q#-: ho% that (and ' 2n )"G circuit power is consumed only in

a'capacitor b' inductor c' resistor d5 0oth 0cC' 2n purely capacitive circuit, the current---

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a' lag the voltage by D!! 05 lead the voltage 0$ c' lead the voltageby %$!! d' lag the voltage by %$!!

' The chock coil is used to control------

a5 A.K b' "G c' both aXb d' non of theseL' )t high frequency of )"G ,the capacitive reactance----

a' e3ains constant b' increases c' decreases d' zero$' The impedance at resonance frequency of series G

circuit,G=!"!%CK(

=$!F

a' C!F 05 >R c' %!!F d' %C!FD' The average value of )"G and voltage over a complete cycle is ----

a'!"L!Ltimes 05 zero c' ma*imum d' minimum%!' hake an electrically charged obHect to and fro produces_"

a' Transverse wave s b' sound waves c5 electro3agnet %aves d'

non%%' 1a*imum of sound wave with electromagnet wave is called ----

a5 Vodulation b' choke c' frequency d' aXb%3' in free space the speed of electromagnetic waves is----------

a5 -) 1>3s1 b' : *%!-$ms-%c' 3"DD * %!-$ms-% c' varying with timeQ#1: A sinusoidal current has r3s value of 1 A. %hat is Va)i3u3 value or pea value?Q#": 9n a U circuit %ill the current lag or lead the voltage? 9llustrate $our ans%ers 0$ vector diagra3.Q#-: E)plain the conditions under %hich electro3agnetic %aves Are produced?

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51635094 2nd Physics Short Ans MCQ

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Transcript of 51635094 2nd Physics Short Ans MCQ