HW6Solns.6Fall2010

# HW6Solns.6Fall2010 - NAME Physics 100 Fa2010 Homework 6...

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NAME: ____________________________________________ Physics 100 Fa2010 Homework 6 Answer Sheet: Due 10/15 in class: Show Your Work for All Problems Chapter 7, Case 7. EXPLAIN all answers!! a. Energy enters as: electrical energy in the current carried through the bulb Energy leaves as: thermal energy as heat leaves the oven through some combination of convection, conduction and radiation b. The units of power are W (Watts) which are equal to J/s (Joules per second) where Joules is a unit of energy. Therefore, if 60W of electrical energy enter the oven, then 60 J/s are entering, and 60 J is entering for each second. c. Since energy is conserved, the entering energy must go into either the thermal energy of the oven itself, which will raise the temperature of the oven according to Δ Q = m c Δ T, or leave the oven as thermal energy. The oven will begin to heat up, but after a time, the temperature will stabilize. After this point, the energy is no longer going into the material of the oven, but is leaving. d. The heat is carried by convection. Hot air rises because it is less dense due to the vigorous motion of the hot molecules. It is therefore less dense than the surrounding cool air. The buoyant force of this hot

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HW6Solns.6Fall2010 - NAME Physics 100 Fa2010 Homework 6...

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