Nace CP 1, Course Manual

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Basic Electricity 1:15
CP 1 – Cathodic Protection Tester Course Manual
©
NACE International, 2000
02/01/05
Now consider the total circuit resistance:
Ω
+
Ω
+
Ω
=
+ +
=
2
1
4
1
5
1
1
R
1
R
1
R
1
1
R
3 2 1
T
Ω = =
+ +
=
05 . 1
0.95
1
0.5 0.25 0.2
1
R
T
A 05 . 19
05 . 1
V 20
I
T
=
Ω
=
The 0.05 discrepancy is due to the decimal in the R
T
calculation.
If all the resistors in a parallel circuit are equal, the total resistance of
the circuit is equal to one of the resistances divided by the number of
resistors.
N
R
R
T
=
where:
R
T
= Total resistance
R = Resistance of each resistor
N = Number of resistors
Turn now to Group Exercise 1.3 for further practice with parallel
circuits.
Series-Parallel Circuit
A series-parallel circuit (Figure 1.8) combines the elements of both a
series circuit and a parallel circuit. Very complex circuits can be
reduced to a circuit consisting of series-parallel elements. This is
important in the design of cathodic protection. The cable running out to
the groundbed represents a series circuit, the groundbed itself a parallel
circuit.