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Physics

Question

Heat and temperature

1. How much heat is required to raise the temperature by 10 degrees Celsius of one kg of water and iron?

2. Two identical objects (the same mass, material) at temperatures T1 = 20 degrees and T2 = 30 degrees are in contact. What is the final temperature of these objects after they reach thermal equilibrium?

 

Solution

1. How much heat is required to raise the temperature by 10 degrees Celsius of one kg of water and iron?

Heat = mass X specific heat capacity X change in temperature
specific heat capacity of water = 1 calorie/ gm / deg Celsius= 4.2 Joules/ gm/ deg Celsius
specific heat capacity of iron = 0.108 calorie/ gm / deg Celsius= 0.45 Joules/ gm/ deg Celsius

One kg= 1000 gm

Heat required for water= 1000 X 4.2 X 10= 42,000 Joules= 42 k J
Heat required for iron= 1000 X 0.45 X 10= 4,500 Joules= 4.5 k J

2. Two identical objects (the same mass, material) at temperatures T1 = 20 degrees and T2 = 30 degrees are in contact. What is the final temperature of these objects after they reach the thermal equilibrium?

For equilibrium heat transferred by one body = Heat received by the other body

M X S X (30- T) = M X S X ( T-20)
M and S will cancel ( same mass and material)
30- T= T -20
or 2 T= 50
or T = 25 degrees at thermal equilibrium

Answer 25 degree is the final temperature.