Angie's house is cold during the winter. she starts a fire in the fireplace to keep the house warm.

how is heat being produced?
a.
by rubbing
b.
by electricity
c.
by burning
d.
by all of these

C

Explanation:

She burns wood in the fireplace

your answer is a. the enthalpy of formation for a pure element in its standard state is always positive.

answer: semi-infinite solid initially at a uniform temperature of 400 ◦c is cooled at its surface by convection. the cooling fluid at a constant temperature of 200 ◦c has a convective coefficient (ha) of 250 w/m2.k. the physical properties of the solid: k = 20 w/m.k and α = 4 * 10-5  m2/s. using δx = 0.04 m and δt = 10 s. write the finite difference equations describing the transient heat transfer of the first five δx and the temperature profile after 30 s.