3 Mehlala ea lipotso mabapi le katoloso ea sebaka
1. Leqephe la tšepe mochesong oa 20 o C le bolelele ba 50 cm le bophara ba 30 cm. Haeba coefficient ea katoloso e otlolohileng ea tšepe e le 10 -5 o C -1 joale keketseho ea sebaka le sebaka sohle mochesong oa 60 o C ke….
Puisano
Hoa tsebahala hore:
Mocheso oa pele (T 1 ) = 20 o C
Mocheso oa ho qetela (T 2 ) = 60 o C
Phetoho ea mocheso (Δ T) = 60 o C – 20 o C = 40 o C
Sebaka sa qalong (A 1 ) = Bolelele x bophara = 50 cm x 30 cm = 1500 cm 2
Koefficient ea katoloso e otlolohileng ea tšepe (α ) = 10 -5 o C -1
Koefficient ea katoloso ea tšepe (β ) = 2a = 2 x 10 -5 o C -1
Potso: Keketseho sebakeng (Δ A )
Keketseho sebakeng (Δ A ):
ΔA = β A 1Δ T
ΔA = ( 2 x 10 -5 o C -1 )(1500 cm 2 )(40 o C)
ΔA = (80 x 10 -5 )(1500 cm 2 )
ΔA = 1 20.000 x 10 -5 cm 2
ΔA = 1.2 x 10 5 x 10 -5 cm 2
ΔA = 1.2 cm 2
Kakaretso ea sebaka ( A 2 ):
A 2 = A 1 + Δ A
A 2 = 1500 cm 2 + 1.2 cm 2
A 2 = 1501 , 2 cm 2
2. Poleiti ea aluminium e nang le coefficient ea katoloso e otlolohileng ea 24 x 10 -6 / o C e na le sebaka sa 40 cm 2 mochesong oa 30 o C. Fumana mocheso oa ho qetela haeba sebaka sa poleiti ea aluminium se eketseha ho fihlela ho 40,2 cm 2.
Puisano
Hoa tsebahala hore:
Mocheso oa pele (T 1 ) = 30 o C
Koefficient ea katoloso e otlolohileng ea aluminium (α ) = 24 x 10 -6 o C -1
Katoloso e lekanang ea sebaka sa aluminium (β ) = 2α = 2 x 24 x 10 -6 o C -1 = 48 x 10 -6 o C -1
Sebaka sa qalong (A 1 ) = 40 cm 2
Sebaka sa ho qetela (A 2 ) = 40,2 cm 2
Phetoho sebakeng (Δ A) = 40,2 cm 2 – 40 cm 2 = 0,2 cm 2
Potso: Fumana mocheso oa ho qetela (T 2 )
Karabo:
Foromo ea phetoho sebakeng (Δ A) :
ΔA = β A 1 Δ T
Mocheso oa ho qetela (T2 ) :
ΔA = β A 1 (T 2 – T 1 )
0,2 cm,2 = (48 x 10-6 oC-1)(40 cm2)(T2 - 30oC)
0,2 = (1920 x 10 -6 ) (T 2 – 30 )
0,2 = (1,920 x 10 -3 ) (T 2 – 30)
0,2 = (2 x 10 -3 ) (T 2 – 30)
0,2 / (2 x 10 -3 ) = T 2 – 30
0,1 x 10 3 = T 2 – 30
1 x 10 2 = T 2 – 30
100 = T 2 – 30
100 + 30 = T 2
T 2 = 130
Mocheso oa ho qetela = 130 o C
3. Ntho e chitja mochesong oa 20 o C e na le radius ea 20 cm. Haeba mochesong oa 100 o C radius e eketseha ho fihlela ho 20,5 cm, joale coefficient ea katoloso e otlolohileng ea ntho ke….
Puisano
Hoa tsebahala hore:
Mocheso oa pele (T 1 ) = 30 o C
Mocheso oa ho qetela (T 2 ) = 100 o C
Phetoho ea mocheso (Δ T) = 100 o C – 30 o C = 70 o C
Radius ea pele (r 1 ) = 20 cm
Radius ea ho qetela (r 2 ) = 20,5 cm
Potso: Koefficient ea katoloso ea sebaka sa ntho ( b )
Karabo:
Sebaka sa pele sa selikalikoe (A 1 ) = π r 1 2 = (3,14)(20 cm) 2 = (3,14)(400 cm 2 ) = 1256 cm 2
Sebaka sa ho qetela sa selikalikoe (A 2 ) = π r 2 2 = (3,14)(20,5 cm) 2 = (3,14)(420,25 cm 2 ) = 1319,585 cm 2
Keketseho sebakeng sa selikalikoe (Δ A) = 1319,585 cm 2 – 1256 cm 2 = 63,585 cm 2
Foromo ea phetoho sebakeng (Δ A) :
ΔA = β A 1 ΔT
Koefficient ea katoloso ea sebaka:
ΔA = β A 1 ΔT
63,585 cm 2 = β (1 256 cm 2 )(70 o C)
63,585 = β ( 87920 o C)
β = 63,585 / 87920 o C
β = 0,00072 / o C
β = 7,2 x 1 0 -4 / o C
β = 7,2 x 1 0 -4 o C -1
Koefficient ea katoloso e otlolohileng (α ):
β = 2 α
α = β / 2
α = (7,2 x 1 0 -4 ) / 2
α = 3,6 x 1 0 -4 o C -1
