Nace CP 1 - Page 40

Basic Electricity 1:17
CP 1 – Cathodic Protection Tester Course Manual
© NACE International, 2000
02/01/05
E
2
R
3
I
T
E
R
4
R
T
Figure 1.9
The total voltage, E
T
= 20 V
Total current flow I
T
= E
T
/R
T
= 20 V/2.00 Ω = 10 A
Next, calculate the voltage across the parallel part of the circuit. This
is equal to the total voltage less the voltage drop across R
4
or
20 V – (10 A x 0.95 Ω) = 10.5 V. Calculating the currents through
R
1
, R
2
, and R
3
is simply a matter of applying Ohm’s Law:
I
1
= 10.5 V/5 Ω = 2.10 A
I
2
= 10.5 V/4 Ω = 2.63 A
I
3
= 10.5 V/2 Ω = 5.25 A
I
T
= 9.98 A
Note that Kirchhoff’s Current Law is fulfilled also. The currents
entering Points A, B, and C equal those leaving these points.