12.4 Electrical Circuits and Components 359
The total current drawn by the circuit is
The total resistance is given by
Note that we could have obtained the total current drawn by the circuit using the total resis-
tance and the Ohm’s law in the following manner:Example 12.6 Determine the total current drawn by the circuit shown in Figure 12.14.
VRtotalItotal 1 9 V 1 1.7 21 Itotal 2 1 Itotal5.3 A
1
Rtotal
1
R 1
1
R 2
1
R 3
1
3
1
7
1
9
1 Rtotal1.7
ItotalI 1 I 2 I 3 3.01.31.05.3 A
9 V
R 2 = 7 R 3 = 9
R 1 = 3
■Figure 12.14 The circuit for Example 12.6.
The circuit given in this example has components that are in both series and parallel
arrangements. We will first combine the light bulbs in the parallel branches into one equiva-
lent resistance.Next, we add the equivalent resistance toR 1 , noting that the two resistors are in series now.
Capacitors
Capacitorsare electrical components that store electrical energy. A capacitor has two oppo-
sitely charged electrodes with a dielectric material inserted between the electrodes. Dielectric
material is a poor conductor of electricity. Capacitors are used in many applications to serve as
filters to protect sensitive components in electrical circuits against power surges. They are also
used in large computer memories to store information during a temporary loss of electric power
to the computer. You will also find capacitors in tuned circuits for radio receivers, audio
filtering applications (e.g., bass and treble controls), timing elements for strobe lights, and inter-
mittent wipers in automobiles.VRtotalItotal 1 9 V 1 6.9 21 Itotal 2 1 Itotal1.3 A
RtotalR 1 Requivalent 3 3.96.9
1
Requivalent
1
R 2
1
R 3
1
7
1
9
1 Requivalent3.9
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