1. (25 pts)
a) (5 pts) Is it correct to say that the current in a circuit is “used up?” Why or why not?
No. Current is not “used up.” Just as much charge returns to the negative terminal of the battery in
the same amount of time as left the positive terminal. This is a consequence of conservation of charge.
b) (5 pts) Explain the fundamental principle behind Kirchhoff ’s Loop Rule (PV= 0).
Kirchhoff’s Loop Rule is based on the principle of Conservation of Energy.
c) (5 pts) Explain what physical process causes the effective resistance of a parallel combination of
resistors to be less than any of the individual resistances.
A parallel combination gives the current a choice of multiple routes. Because the current has multiple
paths, more can flow than through just a single path. From Ohm’s Law, more current indicates a lower
resistance.
d) (5 pts) During operation, the battery in a laptop computer becomes hot. Would this cause an increase
or decrease in the current supplied to the computer? Explain.
Resistance increases as temperature rises (in most materials). Thus the amount of current would
decrease.
e) (5 pts) What is the difference between “physical” and “conventional” current in a metal conductor?
Physical current is the flow of electrons through the conductor. Electrons flow from the negative ter-
minal, through the circuit, to the positive terminal. Conventional Curremt, on the other hand, is
considered the flow of positive charge which is in the opposite direction.
