Question

The inside of a house is at 20°C on an early morning when the temperature outside is 15°C. The next morning the inside temperature is the same but the outside temperature is now 10°C. How much does the energy per unit time lost by conduction through the walls, windows, doors, etc., change for the house from the first morning to the second one?

a) Since the inside temperature stays the same, the loss is the same both days.

b) The loss doubles.

c) The loss halves.

d) The loss increases

Answer 1

in conduction process the amount of heat transfer is directly

proportional to the temperature difference ,area of cross
section and inversely propotional to the thickness

H = dQ/dt = K*A*dT/x

K = coefficient of conductivity

here

on the first day the temperature difference dT1 = 20-15 = 5

on the next day the temperature difference = dT2 = 20-10 = 10

the ramining parameters ar same

so

H2/H1 = dT2/dT1

H2/ H1 = 10/5 = 2

H2 = 2H1

the loss doubles

option b)