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+
R
2
40 kΩ
E
b
R
1
R
3
-
FIGURE 11.40
Illustration for Example 11.33.
■
EXAMPLE 11.33
Problem:
Assume that the current through a resistor of a parallel circuit is known to be 4 milliam-
peres (mA) and the value of the resistor is 40,000 ohms. Determine the potential (voltage) across the
resistor. The circuit is shown in Figure 11.40.
Solution:
Given:
R
2
= 40 kW
I
R
2
= 4 mA
Find
E
R
2
and
E
b
. Select the appropriate equation:
E
=
I
×
R
Substitute known values:
E
R
2
=
I
R
2
×
R
2
E
R
2
= 4 mA × 40,000 ohms
Using power of tens,
E
R
2
= (4 × 10
-3
) × (40 × 10
3
)
E
R
2
= 4.0 × 40
we obtain
E
R
2
= 160 V
Therefore,
E
b
= 160 V
11.7.7.3 Current in Parallel Circuits
In a series circuit, a single current flows. Its value is determined in part by the total resistance of the
circuit; however, the source current in a parallel circuit divides among the available paths in relation
to the value of the resistors in the circuit. Ohm's law remains unchanged. For a given voltage, cur-
rent varies inversely with resistance.
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