Pre-LAB 4 Assignment Fundamentals of Circuits II: Currents ...

Fundamentals of Circuits II: Currents & Circuits v 0.3
x
y
x
Two resistors or bulbs are in series if they are connected so that the
same current that passes through each. In the series connection pictured
to the left, there is only one path available for a current which
runs from x to y.
y
Two resistors or bulbs are in parallel if their terminals are connected
together such that at each junction one end of a resistor or bulb is
directly connected to one end of the other, as at the junctions above
and below the bulbs at the left.
It is important to keep in mind that in more complex circuits, say with three or more
elements, not every element is necessarily connected in series or parallel with other elements.
Let’s compare the behavior of a circuit with two bulbs wired in parallel to the behavior of
a circuit with a single bulb. (See Fig. 6.)
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−
A
+
−
D
E
(a)
(b)
Figure 6: Two different circuits: (a) a single bulb circuit and (b) a circuit with two bulbs
identical to the one in (a) connected in parallel to each other and in parallel to the battery.
Note that if bulbs A, D and E are identical, then the circuit in Fig. 7 is equivalent to circuit
6(a) when the switch is open (as shown) and equivalent to circuit 6(b) when the switch is closed.
Question 2.1 Explain how you know that the caption of Fig. 7 correctly describes the circuit.
Prediction 2.1 Predict how the brightness of bulbs D and E in the parallel circuit of Fig. 6 (b)
will compare to bulb A in the single bulb circuit of Fig. 6 (a). How will D and E compare with
each other? Rank the brightness of all three bulbs. Explain the reasons for your predictions.
PHYS-204:Physics II Laboratory 11