Nace CP 1 - Power; What Is the Current Flow?

Basic Electricity 1:9
CP 1 – Cathodic Protection Tester Course Manual
© NACE International, 2000
02/01/05
What is the current flow?
milliampamps
Ohms
volt
R
E
I 1001.0
1000
0.1
====
Likewise, if we knew the current was 1 milliamp and the voltage was
1.0 volt, what is the resistance?
Ohms
amps
volt
I
E
R 1000
001.0
0.1
===
Note that we had to convert 1.0 milliamp to 0.001 amperes to use
Ohm’s Law since the voltage is in volts, not millivolts.
Ohm's Law plays an important role in your work and you need to be
thoroughly familiar with it. Turn now to Group Exercise 1.1 at the
end of this chapter and work through the calculations in the exercise.
Power
Power is the energy used by an electrical device. It is necessary to
know the power required by a cathodic protection rectifier, for
example, in order to size the alternating current supply circuit.
Power is measured in watts. The equations for power and the
symbols used are:
P = EI
P = I
2
R
where:
P = Power in watts
R = Resistance in Ohms
E = Voltage in volts
I = Current in amperes