1) A heat engine with an efficiency of 40% does 100J of work. How much heat is (
ID: 1602345 • Letter: 1
Question
1) A heat engine with an efficiency of 40% does 100J of work. How much heat is (a) extracted from the hot reservoir and (b) exhausted into the cold reservoir ?
2) Two positive charges of 1.0 nC each are placed at +5cm and -5cm along the y axis. What is the strength and direction of the electric field at a position of a point located at 5cm along the positive x axis ?
3) Large electric fields in cell membranes cause ions to move through the cell wall. The field strength in a typical membrane is 1.0 x 10^7 N/C. What is the magnitude of the force on a calcium ion with a charge of +e ?
4) A 25pF parallel-plate capacitor with an air gap between the plates is connected to a 100v battery. A teflon slab is then inserted between the plates, filling the gap. What is the change in the charge on the positive plate when the teflon is inserted ? (Teflon k = 2 )
Explanation / Answer
1.
efficiency of a heat engine,
= W/Q,
0.4 = 100/Q
Q= 250 J, heat extracted,
Heat rejected, Qj = Q-W = 150J
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