Section b Practicals

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    C.C.H.S. MANSAROVAR PHYSICS PRACTICALS CLASS-XIICODE- E-10/OPTICS/B-1 EXPERIMENT No. Date-..

    Aim- To find the value of v for different values of u in case of a concave mirror and to find the focal length.

    A a!at"#- An optical bench, three uprights, a mirror holder, a concave mirror, two needle, a metre scale and aknitting needle

    Ra$ Dia%!am

    &o!m"'a (#e)- The focal length f of a concave mirror is related to the object distance u and image distance v by the

    formula1

    f =

    1

    u+

    1

    v (mirror formula) or f =

    uvu+ v

    , or a concave mirror both object distance u and

    image distance v are negative. !ence focal length is also negative.

    O*#e!+atio,#-Ste -1 To )ete!mi,e !o"% o a' 'e,%t ."ough focal length of the concave mirror = ###### cm

    Ste - Ta*'e o! i,)i,% " + 1/" 1/+

    $l.%o.

    &osition of upright with 'bserved distance

    oncave mirror & (cm)

    'bjectneedle '(cm)

    mageneedle (cm)

    &' = u(cm)

    & = v(cm)

    *+u(cm * )

    *+v(cm * ) f =

    uvu + v

    (cm)*.-.

    ./.0.1.

    2ean focal length of concave mirror f = ## cm

    Ca' "'atio,# 3 *. f =uv

    u + v = ###. cm

    pg. 1

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    C.C.H.S. MANSAROVAR PHYSICS PRACTICALS CLASS-XII$imilarly, make calculations of focal length f for other observations and take the mean of all the focal lengths.

    . &!om t e %!a *et2ee, " a,) + 4 &lot graph betweenu (cm) and v (cm) by choosing appropriate scales along5 / a6is and 7 / a6is as shown in ig. The graph comes out to bea rectangular hyperbola. 8raw the right bisector '9 of theangle : 5 / ' 7 / meeting the graph at 9.

    rom 9, draw 9A and 9; perpendiculars on 5 / and 7 / a6esrespectively.

    rom the graph of ig. , we have 'A = ##.. cm, and'; = ###.. cm. Thereforef = 'A+- = #.. cm and ';+-= ## cm. 2eanfocal length, f = ##.. cm.

    3. &!om t e %!a *et2ee, 1/" a,) 1/+ 4 &lot graph between*+u (cm) and *+v (cm) by choosing appropriate scales along5 / a6is and 7 / a6is as shown in ig. The graph comes out to bea straight line e

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    C.C.H.S. MANSAROVAR PHYSICS PRACTICALS CLASS-XII

    CODE- E- 0/Semi o,)" to!/B-11 EXPERIMENT No. Date-..Aim- To study the characteristic of a common n p n or p n p transistor and to find out the values of current andvoltage gains.

    A a!at"#- A ,- p n transistor, a volt battery, or a power supply ( >) , a milliammeter (range to 0 mA), arnicro ammeter (range to 0 ?A), two one way key or switch. Two high resistances, connecting wires and a pieceof sand paper.Ci! "it Dia%!am

    &o!m"'a "#e) (i) i, "t !e#i#ta, e R i 4

    | V BE

    I B |V CE = constant

    4 1

    I B/ V BE 4

    1

    slpoeof input characteritics

    (ii) o"t "t !e#i#ta, e R 0 4 | V CE I C | I B = constant 4 1 I C / V CE 4 1slpoeof output characteritics(iii) C"!!e,t %ai, 5 4 | I C I B|V CE = constant 4 #'o e o t!a,# e! a!a te!i#ti #(iv) Vo'ta%e %ai, A V 4 5

    R0 Ri

    4 "!!e,t %ai, 6 !e#i#ta, e %ai,

    O*#e!+atio,#Ste -1. To )ete!mi,e 'ea#t o",t# o +a!io"# i,#t!"me,t#

    @east count of voltmeter > ; = #####. > @east count of voltmeter > = #####. > @east count of microammeter ; = #####.?A @east count of milliammeter = ##### mA

    Ste - . Ta*'e o! i, "t a!a te!i#ti #$.%o. ;ase emitter

    voltage ( > ; ) ;ase current ( ; ) in (?A) for

    in (volt) > = - > > = / >

    *.-.

    ./.

    pg. 3

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    C.C.H.S. MANSAROVAR PHYSICS PRACTICALS CLASS-XII0.1.B.C.

    Ste -3. Ta*'e o! o"t "t a!a te!i#ti #

    $.%o. ollector emitter

    voltage ( > )

    ollector current ( ) in (?A) for

    in (volt) ; = * ?A ; = - ?A ; = ?A ; = / ?A*.-.

    ./.0.1.B.C.

    Ste -7. Ta*'e o! t!a,# e! a!a te!i#ti #

    $.%o. ;ase current( ; )

    ;ase current ( ) in (mA) for

    in (?A) > = - > > = / >*.-.

    ./.0.1.B.

    C.

    Ca' "'atio,#

    *. I, "t Re#i#ta, e R i 8 !om i, "t a!a te!i#ti #9 4 ;yselecting suitable scales, plot > ; along 5 a6is and ; along7 a6is for a constant value of > . 'n the same graph sheet,

    plot another curve for the ne6t (constant) value of > . Theseare input characteristics as shown in ig. rom a point& on the input characteristics, calculate the inputresistance as follows. R i 4

    | V BE I B |V CE = constant 4

    AC BC 4 ##.. D

    pg. 4

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    C.C.H.S. MANSAROVAR PHYSICS PRACTICALS CLASS-XII

    - . O"t "t Re#i#ta, e R o 8 !om o"t "t a!a te!i#ti #9 4;y selecting suitable scales, plot > along 5 a6is and along 7 a6isfor a constant value of ; . 'n the same graph sheet, plot anothercurve for the other (constant) value of ; . These are outputcharacteristics as shown in ig. rom a point & on the outputcharacteristics, calculate the output resistance asfollows.

    R o 4 | V CE I C | I B = constant 4 AC BC 4 ##.. D

    . C"!!e,t :ai, 8 !om t!a,# e! a!a te!i#ti #9 4 ;y selectingsuitable scales, plot a graph between base current ; along 5 a6is andcollector current along 7 a6is. This graph representstransfer characteristics as shown in ig. rom the graph,calculate current gain as follows 4

    urrent Eain,

    5 4 | I C I B|V CE = constant 4 BC AC 4 ##..

    /. Vo'ta%e %ai, A V 4 5

    R0

    Ri 4 #####.

    Re#"'t-

    l. Thc input, output and transfer characteristics are shown in the adjoining graphs.-. The current gain and voltage gain of the given transistor are ###. and ...........

    P!e a"tio,#

    . All the measuring instruments for current and voltage should be of proper range.-. ;atteries should be connected carefully with proper polarities, keeping in mind whether the given transistor is p n p

    or n p n.. ;efore switching on the power supplies, the sliders " * and " - of the potentiometer should be set at the minimumvalues./. %ever e6ceed the ratings for the currents given in the transistor manual.

    pg. 5

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    C.C.H.S. MANSAROVAR PHYSICS PRACTICALS CLASS-XII

    CODE- E-;/E'e t/A-; EXPERIMENT No. . Date-

    Aim- To convert the given galvanometer (of known resistance and figure of merit) into an ammeter of desired rangeand to verify the same.

    A a!at"#- A Feston type galvanometer (of known resistance and figure of merit), a manganin or constantan wire,

    screw gauge, a battery, a one way key, a rheostat, a milli ammeter of 0 mA range, connecting wires and sand paper.

    Ci! "it Dia%!am 8 o! Ve!i i atio,9

    &o!m"'a "#e)- (i) A galvanometer of resistance E and figure of merit k or current for full scale deflection g (=%k)can be converted into an ammeter of range ampere by connecting shunt resistance $ in parallel with it. The value

    of shunt $ is given by $ = ( I g

    I I g ) E =

    G

    ( I I g) 4G

    n 1 where n =

    I I g

    = conversion ratio

    (ii) The length ( l ) of the wire to be used as shunt can be calculated using the relation $ = Gl

    r2 o! l 4

    r2S

    where r is the radius of the given wire and G is its specific resistance or resistivity.

    O*#e!+atio,#-Ste '. To determine shunt resistance $"esistance of the given galvanometer, E = ##.. D

    igure of merit, k = .........A+divTotal number of divisions on either side of Hero, % = ###..

    urrent re

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    C.C.H.S. MANSAROVAR PHYSICS PRACTICALS CLASS-XII@east count =

    pitch No . of divisiononC . S .

    = ##### cm.

    %o. of divisions on . $.Ieto error. e = .........cmIero correction. c = e =.......cm.Ta*'e o! )iamete! o t e 2i!e

    $.%o. 2ain scalereadinga (cm)

    ircular scalereading n raction to be added b = n 6 (@. .) 'bserved diameter d = a J b

    *. a b-. a b

    . a b

    2ean observed diameter, d = ## cm2ean corrected diameter, d = d J c = ## cm2ean corrected radius, r = d+- = ### cm$pecific resistance of material of the wire, G = #### ohm cm( G manganin = // 6 * 1 ohm cm and G constantan = /K 6 * 1 ohm cm)

    The reerification (for checking the accuracy of the converted ammeter)"ange of conversion of the ammeter, = ....... ATotal number of divisions on either side of Hero, % = ##..@east count of the converted ammeter, k / = +% = ###.. A+div

    Ta*'e o! +e!i i atio,$l.%o.

    Ealvanometer reading Ammeter reading (A)

    rror ( +)(A)

    L rror I I

    I

    ) 6*8eflection(M) (division)

    urrent/ =k + M

    *.-.

    ./.

    Re#"'t- As the difference ( 3 +) is very small, therefore , the galvanometer is properly converted into ammeter of therange.

    P!e a"tio,#l. The diameter of the wire (to be used as shunt) should be measured accurately.-. @ength of the shunt wire should be neither too large or too small.

    . The length of the wire should be - cm more than the calculated value l . The shunt wire should be connectedcarefully across the galvanometer terminals such that e6actly length l (i. e., the marked points) of the wire should

    just come out of the terminals of the galvanometer./. The different parts of the shunt wire should not touch each other.0. The ammeter used for verification should preferably of the same range as the range of the converted of ammeter.1. Any Hero error in the galvanometer or ammeter should be eliminated or taken into account properly.

    pg. 7

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    C.C.H.S. MANSAROVAR PHYSICS PRACTICALS CLASS-XII