genius by Pradeep Kshetrapal Transmission Transmission of Heat 159
Problems based on conduction Basic level 1.
Mud houses are cooler in summer and warmer in winter because [MP PAT 1996; BVP 2003]
2.
(a) Mud is superconductor of heat heat
(b)
Mud is good conductor of
(c) Mu Mud is bad conductor of heat
(d)
None of these
Heat current is maximum in which of the following (rods are of identical dimension) Copper
(a) 3.
(b)
Copper Steel
(c)
Steel Copper
[Orissa JEE 2003]
(d)
Steel
Consider the following statements Assertion (A) !oolen clothes "eep the body warm in winter Reason (R) (R) #ir is a bad conductor of heat $f these statements
[AIIMS 2002]
(a) %ot %oth A and A and R are true and the R is a correct explanation of the A the A (b) %ot %oth A and A and R are true but the R is not a correct explanation of the A the A (c) A is A is true but the R is false (d) %ot %oth A and A and R are false (e) A is A is false but the R is true 4.
The lengths and radii of two rods made of same material are in the ratios & ' and ' respectiely respectiely** +f the temperature temperature di,erence di,erence between the ends for the two rods be the same then in the steady state* The amount of heat -owing per second through them will be in the ratio [MP PET 2000]
(a) & 5.
(b) .
(c) / 0
(d) '
Two Two essels of di,eren di,erentt materials are similar similar in si1e in eery eery respect* respect* The same 2uantity 2uantity of ice 3lled in them them gets melted in '4 minutes and 4 minutes* The ratio of their thermal conductiities will be [MP PMT 1989; CMEET Bihar 1995]
(a) &*5 6.
(b) &
(c) '6
(d) .
+f the coe7cient of conductiity of aluminium is 4*5 cal/cm-sec-oC, then in order to conduct &4 &4 cal/sec-cm cal/sec-cm' in the steady state8 the temperature gradient in aluminium must be [MP PAT PAT 1990] 199 0] o
(a) 5 C/cm .
(c) '4oC/cm
(d) (d) &4*5oC/cm
The area of the glass of a window of a room is &4m &4 m'* and thic"ness ' mm* mm* The outer and inner temperature temperature are o o .4 C and '4 C respectiely* Thermal conductiity of glass in MKS system MKS system is 4*'* The heat -owing in the room per [MP PMT 1989] second will be (a) 9 &4. Joules
8.
(b) &4oC/cm
(b) ' 9 &4. Joules
(c) 4 Joules
(d) .5 Joules
!hen two ends of a rod wrapped with cotton are maintained at di,erent temperatures and after some time eery point of the rod attains a constant temperature8 then [MP PET !PMT 1988]
(a) Conduction of heat heat at di,erent di,erent points of the rod stops stops because the temperature temperature is not increasing increasing (b) :od :od is bad bad condu conductor ctor of of heat heat (c) Heat is being being radiated radiated from from each each point of the the rod
genius 160 Transmission of Heat (d) ;ach point of the rod is giing heat to its neighbour at the same rate at which it is receiing heat 9.
+n which case the thermal conductiity increases from left to right ["CE#T 194$ 6]
(a) Al, Cu, Ag
(b) Ag, Cu, Al
(c) Cu, Ag, Al
(d) Al, Ag, Cu
10. To a rough approximation8 conductiities of metals are about (a) &444 times as those of li2uids and &48444 times of gases (b) &4 times as those of li2uids and &44 times of gases (c) &44 times as those of li2uids and &444 times of gases (d) &48444 times as those of li2uids and &444 times of gases 11.
# copper bar &4 cm long has its ends pressed against copper tan"s at 4 oC and &44 oC* The ends are separated by layers of dust 4*& mm thic"* +f conductiity of dust is 4*44& times that of copper8 the temperatures of end P and Q of bar are
(a) * oC and >>*? oC o
&44oC
o
(b) >>*? C and * C o
4oC Q
P
o
(c) ?5 C and '5 C (d) >4 oC and .4 oC
Problems based on combination of conductors Basic level 12. Three rods of the same dimension hae thermal conductiities K 8 'K and K * They are arranged as shown in 3gure gien below8 with their ends at &44 4C8 544C and '44C* The temperature of their @unction is [%PSEAT 2002] 54oC
(a) >4o
'K &44oC
(b) ?4o
K
(c) 54o
K
'4oC
o
(d) 5 13.
Aie rods of same dimensions are arranged as shown in the 3gure* They hae thermal conductiities K &8 K '8 K 8 K . and K 5* !hen points A and B are maintained at di,erent temperatures8 no heat -ows through the central rod if [&CET 2002]
C K &
(a) K & B K . and K ' B K
K ' K 5
A
(b) K & K . B K ' K
K
(c) K & K ' B K K .
B K .
D
(d) 14.
K & K .
K ' =
K (
# wall has two layers A and B each made of di,erent materials* The thic"ness of both the layers is the same* The o thermal conductiity of A, K ABK B. The temperature di,erence across the wall is '4 C in thermal e2uilibrium [CPMT 1998]
(a) The temperature di,erence across A is &5oC (b) :ate of heat transfer across A is more than across B (c) :ate of heat transfer across both is same
genius by Pradeep Kshetrapal Transmission of Heat 161 (d) Temperature di,erence across A is 5 oC 15. Two metal cubes A and B of same si1e are arranged as shown in the 3gure* The extreme ends of the combination are maintained at the indicated temperatures* The arrangement is thermally insulated* The coe7cients of thermal conductiity of A and B are 44 W/m oC and '44 W/m oC, respectiely* #fter steady state is reached8 the [IIT'JEE 1996] temperature t of the interface will be t
(a) .5oC (b) 04oC
&44oC
(c) 4oC
4oC
B
A
K &
K '
(d) >4oC 16. Two cylinders P and Q hae the same length and diameter and are made of di,erent materials haing thermal conductiities in the ratio ' * These two cylinders are combined to ma"e a cylinder* $ne end of P is "ept at &44oC and another end of Q at 4oC* The temperature at the interface of P and Q is [MP PMT 1994]
(a) 4oC
(b) .4oC
(c) 54oC
(d) >4oC
1. Two identical plates of di,erent metals are @oined to form a single plate whose thic"ness is double the thic"ness of each plate* +f the coe7cients of conductiity of each plate are ' and respectiely8 then the conductiity of composite plate will be [MP PAT 1990] (a) 5 18.
(b) '*.
(c) &*5
(d) &*'
Aour identical rods of same material are @oined end to end to form a s2uare* +f the temperature di,erence between the ends of a diagonal is &44 oC8 then the temperature di,erence between the ends of other diagonal [MP PET 1989] will be (a) 4oC
(c)
&44
(b) o
'l
C
&44 l
o
C where l is the length of each rod
(d) &44oC
19. Two identical rods of metal are welded end to end as shown in 3gure (a)* '4 calories of heat -ows through it in . minutes* +f the rods are welded as shown in 3gure (b)8 the same amount of heat will -ow through the rods in ["CE#T 1982] &44oC
4oC
(a) & minute
(a)
(b) ' minutes
4oC
&44oC
(c) . minutes (b)
(d) &> minutes
20. Two bars of thermal conductiities k and k and lengths & cm and ' cm respectiely hae e2ual crossDsectional area8 they are @oined lengths wise as shown in the 3gure* +f the temperature at the ends of this composite bar is 4oC and &44 oC respectiely8 then the temperature φ of the interface is (a) 54oC (b)
&44 o (
φ
C
(c) >4oC (d)
'44 o
o
4C
K
K
& cm
' cm
&44oC
C
(
21. Three rods A, B and C hae the same dimensions* Their thermal conductiities are K #8 K % and K C respectiely* A and B are placed end to end8 with their free ends "ept at a certain temperature di,erence* C is placed
genius 162 Transmission of Heat separately8 with its ends "ept at the same temperature di,erence* The two arrangements conduct heat at the same rate* K C must be e2ual to (a) K A + K B
(b)
K A K B K A
+ K B
(c)
& '
(K A
+
K K K + K
(d) '*
K B )
A
B
A
B
22. The three rods described in the preious 2uestion are placed indiidually8 with their ends "ept at the same temperature di,erence* The rate of heat -ow through C is e2ual to the rate of combined heat -ow through A and B* K C must be e2ual to (a) K A + K B
(b)
K A K B K A
+ K B
(c)
& '
(K A
+
K K K + K
(d) '*
K B )
A
B
A
B
23. Three rods A, B and C of the same length and crossDsectional area are @oined in series as shown in the 3gure* Their thermal conductiities are in the ratio & ' &*5 * +f the open ends of A and C are at '44 oC and &/ oC8 respectiely8 the temperature at @unction of A and B in e2uilibrium is '44oC
(a) ?. oC (b) &&> oC (c) &5> oC
&/oC
K
'K
&*5K
A
B
C
(d) &./ oC
Advance level 24. Three rods of identical area of crossDsection and made from the same metal form the sides of an isosceles triangle ABC. right angled at B* The points A and B are maintained at temperatures T and
'T
respectiely* +n
the steady state the temperature of the point C is T C* #ssuming that only heat conduction ta"es place8 e2ual to (a)
T C T
is
[IIT'JEE 1995]
&
(b)
( ' + &)
( ' + &)
(c)
& '( '
&
(d)
− &)
( '
− &)
25. Three rods of material and three rods of material ! are connected as shown in 3gure* #ll are identical in length and crossDsectional area* +f end A is maintained at >4oC, end " at &4oC, thermal conductiity of is 4*0' cal/seccm-oC and that of ! is 4*.> cal/sec-cm-oC, then 3nd the temperature of @unctions B, C, D C
o
o
o
(a) '4 C8 4 C8 '4 C
>4 C
(b) 4oC8 '4oC8 '4oC
A
o
o
o
&4oC "
! B !
o
(c) '4 C8 '4 C8 4 C
! D
(d) '4oC8 '4oC8 '4oC 26.
Aie rods &8 '8 8 .8 5 are connected to form the letter # as shown in the 3gure* The rods are of same length and radii but haing conductiities in the ratio K & K ' K K . K 5 B & & ' ' * The uniform temperature of the rod 5 in the steady state is (a)
&
&44 o
C &44oC '
(b) 54oC
4oC
5 .
(c) >4oC (d)
'44 o (
C
Miscellaneous problems based on conduction
genius by Pradeep Kshetrapal Transmission of Heat 163
Basic level 2. There are two identical essels 3lled with e2ual amounts of ice* The essels are of di,erent metals* +f the ice melts in the two essels in '4 and 5 minutes respectiely the ratio of the coe7cients of thermal conductiity of [MP PET 2001] the two metals is (a) . ?
(b) ? .
(c) &> .0
(d) .0 &>
28. Temperature at the surface of la"e is E'4 oC* Then temperature of water @ust below the lower surface of ice layer is [#PET 2000] (a) E .o C
(b) 4o C
(c) .o C
(d) E '4o C
29. Two identical rods of copper and iron are coated with wax uniformly* !hen one end of each is "ept at temperature of boiling water8 the length upto which wax melts are /*. cm and .*' cm respectiely* +f thermal conductiity of copper is 4*0'8 then thermal conductiity of iron is [MP PET 1995]
(a) 4*' 30.
(b) 4*.>
(c) The water has large latent heat of fusion la"e is high
(b)
The water has large speci3c
(d) The temperature of the earth at the bottom of the
+f the steady thic"ness of ice layer is &44 cm and that of water is .*'4 m in a la"e of a cold country where temperature of air is E 5*4oC and temperature of water at the bottom is . oC* The ratio of the thermal conductiity of water to that of ice is (a) .
32.
(d) 4*>0
Furing seere winter in the low temperature 1ones of the world8 the super3cial parts of the la"es are fro1en8 leaing water below* The free1ing at the bottom is preented because (a) The conductiity of ice is low heat
31.
(c) 4*&&5
(b) .*'5 &
(c) &
(d) 5*'5 &
# &4 cm layer of ice has been formed oer a pond of water* The temperature of air aboe is E5 oC* How long will it ta"e the layer to become &4*& cm thic"G (ien K ice B 4*44/ C$S units8 density of ice B & gm/cc and %ice B /4 cal/gm) (a) '445 sec
(b) &?45 sec
(c) &.45 sec
(d) ?45 sec
Problems based on convection Basic level 33.
$ne feels hotter at the top of a -ame than the sides because of [AIIMS 2000]
(a) Conduction 34.
(c) :adiations
(d) %oth IaI and IcI
Mode of transmission of heat8 in which heat is carried by the moing particles8 is (a) :adiation
35.
(b) Conection
(b) Conduction
(c) Conection
[&CET (M)*.+ 1999]
(d) !ae motion
!hile measuring the thermal conductiity of a li2uid8 we "eep the upper part hot and lower part cool8 so that [CPMT 1985; MP PMT ! PET 198 8]
(a) Conection may be stopped (c) Heat conduction is easier downwards
(b)
:adiation may be stopped
(d) +t is easier and more conenient to do so
36. The layers of atmosphere are heated through (a) Conection
(b) Conduction
[MP PET 1986]
(c) :adiation
(d) (b) and (c) both
3. The rate of loss of heat from a body cooling under conditions of forced conection is proportional to its (#) heat capacity (%) surface area (C) absolute temperature (F) excess of temperature oer that of surrounding state if ["CE#T 1982]
(a) #8 %8 C are correct
(b) $nly A and C are correct (c) $nly B and D are correct
(d)
$nly D is correct
genius 164 Transmission of Heat
Problems based on radiation Basic level 38.
Heat traels through acuum by [AIIMS 1998; CPMT 2003]
(a) Conduction 39.
(b) Conection
(c) :adiation
Aor a perfectly blac" body8 its absorptie power is
(d) %oth (a) and (b) [MP PMT 1989$ 92; #PET 2001$ 03; A,MC
2003]
(a) & 40.
(b) 4*5
(c) 4
(d) +n3nity
!hich of the following is the example of ideal blac" body [AIEEE 2002]
(a) Ka@al 41.
(b) %lac" board
(c) # pin hole in a box
(d) None of these
!hich of the following is the best example of an ideal blac" body [CBSE PMT 2002]
(a) Jamp blac"
(b) Platinum blac"
(c) Highly heated charcoal lamp constant temperature
(d)
Caity
maintained
42. The spectrum from a blac" body radiation is a
at
[MP PMT 1989; #PET
2000]
(a) Jine spectrum both 43.
(b) %and spectrum
(d) Jine and band spectrum
+n summer one feels cold on entering an air conditioned room* This can be explained by (a) NewtonIs law o& cooling
(b)
(c) Kircho,Is law 44.
(c) Continuous spectrum
tefanIs law
(d) PreostIs theory of heat exchange
$ut of the radiations falling on surface of a body8 4L radiations are absorbed and 4L are transmitted then its re-ection coe7cient will be (a) 4*
(b) 4*>
(c) 4*.
(d) ero
Problems based on Kircho's law Basic level 45. There is a blac" spot on a body* +f the body is heated and carried in dar" room then it glows more* This can be explained on the basis of [#PET 2000]
(a) NewtonIs law of cooling tefanIs 46.
(b)
!ienIs law
(c) Kircho,Is law
(d)
+f between waelength λ and λ + ' λ 8 eλ and aλ be the emissie and absorptie powers of a body and " λ be the emissie power of a perfectly blac" body8 then according to Kircho,Is law8 which is true [MP PET 1991]
(a) eλ
=
aλ
=
"λ
(b) eλ "λ
= aλ
(c) eλ
= aλ "λ
(d) eλ aλ "λ = co(sta(t
4. The 3gure shows two similar sheets of tin plate8 one polished and the other painted dull blac"* # piece of cor" is attached on the reerse side of each plate by means of melted para7n wax* !hat will happen when an electric bulb placed exactly midway between them is switched on Full blac"
Polished
(a) The cor" on the polished plate falls o, 3rst (b) The cor" on the dull blac" plate falls o, 3rst (c) %oth cor"s fall o, at the same time (d) Neither cor" falls o, 48.
Furing total solar eclipse Araunho,erIs lines appear bright because
Cor"
!ax
Cor"
!ax
genius by Pradeep Kshetrapal Transmission of Heat 165 (a) Moon totally coers both parts of sun photo sphere and chromosphere (b) un light is scattered by moon (c) Moon bloc"s the radiations emitted by chromosphere (d) Moon bloc"s the radiations emitted by photosphere and radiations emitted by chromosphere reach the earth
Problems based on Stefan's law Basic level 49.
# blac" body radiates energy at the rate of " )att/m' at a high temperature T K. !hen the temperature is reduced to
T '
K 8 the radiant energy will be [CPMT 1988; M"# 1993; SC#A 1996; MP PAT 1990; MP PMT 1992; M- CET 2001]
(a) 50.
" &>
.
(c) . "
(d) &> "
(b) 0Q
(c) '?Q
(d) /&Q
# blac" metal foil is warmed by radiation from a small sphere at temperature T and at a distance '* +t is found that the power receied by the foil is IPI* +f both the temperature and the distance are doubled8 the power [MP PMT 199] receied by the foil will be (a) &> P
52.
"
#t temperature T 8 the power radiated by a body is Q )atts* #t the temperature T the power radiated by it will be [MP PET 2000] (a) Q
51.
(b)
(b) . P
(c) ' P
(d) P
# solid sphere and a hollow sphere of the same material and si1e are heated to the same temperature and allowed to cool in the same surroundings* +f the temperature di,erence between each sphere and its [Mai/a MEE 1995] surroundings is T 8 then (a) The hollow sphere will cool at a faster rate for all alues of T (b) The solid sphere will cool at a faster rate for all alues of T (c) %oth spheres will cool at the same rate for all alues of T (d) %oth spheres will cool at the same rate only for small alues of T
53. Two bodies A and B hae thermal emissiities of 4*4& and 4*/& respectiely* The outer surface areas of the two bodies are the same* The two bodies emit total radiant power at the same rate* The waelength λ B corresponding to maximum spectral radiancy in the radiation from B is shifted from the waelength corresponding to maximum spectral radiancy in the radiation from A8 by &*44 µ m * +f the temperature of A is [IIT'JEE 1994] 5/4' K
= &*5 µ m
(a) The temperature of B is &0. K
(b) λ B
(c) The temperature of B is &&>4. K
(d) The temperature of B is '04& K
54. The temperature of a piece of iron is '? oC and it is radiating energy at the rate of Q kW mE'* +f its temperature is raised to &5&oC8 the rate of radiation of energy will become approximately [MP PET 1992]
(a) 'Q kW mE' 55.
(b) .Q kW mE'
(c) >Q kW mE'
(d) /Q kW mE'
+f " is the total energy emitted by a body at a temperature T K and "max is the maximum energy emitted by it at the same temperature8 then [MP PAT 1990]
(a) " ∝ T . C "max ∝ T 5 (b) " ∝ T . C "max ∝ T −5 56.
(c) "
∝ T −. C "max ∝ T .
(d) "
∝ T 5 C "max ∝ T .
# metal ball of surface area '44 cm' and temperature 5'?oC is surrounded by a essel at '? oC* +f the emissiity of the metal is 4*.8 then the rate of loss of heat from the ball is (σ
=
5*>?× &4−/ J 6 m' − s − K . )
[MP PMT ! PET 1988]
(a) &4/ Joules appro*.
(b) &>/ Joules appro*.
(c) &/' Joules appro*.
(d) &0' Joules appro*.
genius 166 Transmission of Heat 5.
+f the rates of cooling of two bodies are same then for which body the rate of fall of temperature will be moreG Aor the body whose thermal capacity is (a) More
(b) Jess
(c) +n3nity
(d) #ny alue
Advance level 58.
+f a sphere of radius R8 cube of side R, and a cylinder of radius R and height R made of same substance are heated to same temperature and then cooled8 then which of aboe will radiate maximum (a) Cylinder
(b) phere
(c) Cube
(d) Cylinder and sphere both
59. The temperature of an isolated blac" body falls from T & to T ' in time t * Jet c be a constant
& − T '
(a) t = c 60.
& & − T '' T &'
T & &
(b) t = c
& & − T '( T &(
(c) t = c
& & − T '. T &.
(d) t = c
# sphere of density '8 satis3ed heat s and radius r is hung by a thermally insulating thread in an enclosure which is "ept at a lower temperature than the sphere* The temperature of the sphere starts to drop at a rate which depends upon the temperature di,erence between the sphere and the enclosure* +f the temperature di,erence is ∆T and surrounding temperature is T 4 then rate of fall in temperature will be (ien that ∆T <<
.σ T 4 ∆T (
(a)
&'σ T 4 ∆ T (
(b)
r'c
r'c
&'σ T 4 ∆T .
(c)
(d)
T 4)
&'σ ∆T r'cT 4
r'c
Problems based on ewton's law of coolin! Basic level 61.
#ccording to NewtonIs law of cooling8 the rate of cooling of a body is proportional to
( ∆θ ) ( 8 where
∆ θ
is the
di,erence of the temperature of the body and the surroundings and ( is e2ual to [AIEEE 2003]
(a) +(e 62.
(b) T)o
The latent heat of gases
[CPMT 193$ 2002]
(c) peci3c heat of li2uids (d)
Ji2uid is 3lled in a essel which is "ept in a room with temperature '4 oC* !hen the temperature of the li2uid is /4oC8 then it loses heat at the rate of >4 cal/sec. !hat will be the rate of loss of heat when the temperature of [MP PMT 1994] the li2uid is .4 oC (a) &/4 cal/ sec
64.
(d) our
NewtonIs law of cooling is used in laboratory for the determination of the (a) peci3c heat of the gases(b) Jatent heat of li2uids
63.
(c) Tree
(b) .4 cal/ sec
(c) 4 cal/ sec
(d) '4 cal/ sec
# buc"et full of hot water is placed in a room* !ater ta"es t & seconds to cool from 04 oC to /4oC8 t ' seconds to cool from /4oC to ?4oC and t seconds to cool from ?4 oC to >4oC then [CBSE PMT 1995; PMT 1993]
(a) t t ' t & 65.
(b) t & t ' t
(c) t & t ' t
(d) t & t ' t
# calorimeter of negligible water e2uialent contains .4 gm of water and it cools at the rate of 4*'. oC per minute in the surroundings at 4 oC. +f at any moment the temperature of water is . oC then at what rate the heat should be supplied to it to "eep its temperature constant (a) 4*'. Cal/m0(ute
(b) &44 Cal/m0(ute
(c) &4*' Cal/m0(ute
(d) None of the aboe
Advance level 66.
# body cools in a surrounding which is at a constant temperature of θ 4 * #ssume that it obeys NewtonIs law of cooling* +ts temperature θ is plotted against time t * Tangents are drawn to the cure at the points P (θ = θ &) and Q(θ = θ ') * These tangents meet the time axis at angles of φ ' and φ & 8 as shown
genius by Pradeep Kshetrapal Transmission of Heat 16 (a)
(b)
(c)
(d) 6.
tanφ ' tanφ & tanφ ' tanφ &
θ & θ 4 θ ' θ 4 −
=
θ
−
θ '
θ ' θ 4 θ & θ 4 −
=
tanφ & tanφ ' tanφ & tanφ '
P
θ &
Q
−
=
θ & θ '
=
θ ' θ &
θ 4
φ '
φ & t
# system S receies heat continuously from an electrical heater of power &4 W * The temperature of S becomes constant at 54oC when the surrounding temperature is '4 oC* #fter the heater is switched o,8 S cools from 5oC to .*/oC in & minute* The heat capacity of S is (a) &44 J/ oC
(b) 44 J/ oC
(c) ?54 J/ oC
(d) &544 J/ oC
Problems based on "ein's displacement law Basic level 68.
# blac" body has maximum waelength λ m at temperature '444 K * +ts corresponding waelength at temperature 444 K will be [CBSE PMT 2001]
(a) 69.
( '
λ m
(b)
' (
λ m
(c)
. 0
λ m
(d)
0 .
λ m
Consider the following statements Assertion (A) !hen temperature increases8 the colour of a star shifts towards smaller waelength8 i*e*8 towards iolet colour Reason (R) :ed colour has maximum waelength $f these statements
[AIIMS 2000]
(a) %oth A and R are true and the R is a correct explanation of the A (b) %oth A and R are true but the R is not a correct explanation of the A (c) A is true but the R is false (d) %oth A and R are false (e) A is false but the R is true 0. The waelength of radiation emitted by a body depends upon [MP PMT 1992]
1.
(a) The nature of its surface
(b)
The area of its surface
(c) The temperature of its surface
(d)
#ll the aboe factors
$n inestigation of light from three di,erent stars A, B and C8 it was found that in the spectrum of A the intensity of red colour is maximum8 in B the intensity of blue colour is maximum and in C the intensity of yellow colour is maximum* Arom these obserations it can be concluded that [CPMT 1989]
(a) The temperature of A is maximum8 B is minimum and C is intermediate (b) The temperature of A is maximum8 C is minimum and B is intermediate (c) The temperature of B is maximum8 A is minimum and C is intermediate (d) The temperature of C is maximum8 B is minimum and A is intermediate 2.
+f blac" wire of platinum is heated8 then its colour 3rst appear red8 then yellow and 3nally white* +t can be understood on the basis of
genius 168 Transmission of Heat [MP PMT 1984]
(a) !ienIs displacement law exchange
(b)
Preost
theory
(c) NewtonIs law of cooling
(d)
None of the aboe
of
heat
Problems based on ener!# distribution !raph Basic level 3.
hown below are the blac" body radiation cures at temperatures T & and T ' (T 'T &)* !hich of the following plots is correct [AIIMS 2003] T '
1
(a)
T '
1
(b)
T &
λ
T '
1
(c)
T &
(d)
T &
λ
T &
1
λ
T '
λ
4. The spectrum of a blac" body at two temperatures '? oC and '?oC is shown in the 3gure* Jet A& and A' be the areas under the two cures respectiely* The alue of (a) & &> (b) . & (c) ' & (d) &> &
A' A&
y t
is i s
n e t n +
' '?oC &
'?oC !aelengt h