Basic Electricity 1:7
CP 1 – Cathodic Protection Tester Course Manual
© NACE International, 2000
02/01/05
Electric Circuit
The electric circuit is the path followed by an electric current. See
Figure 1.2. Examples of various circuits are shown in Figures 1.6,
1.7 and 1.8.
+
E
R
I
Figure 1.2 Basic DC Electrical Circuit
Electrical Laws
Electrical laws govern the relationships in electric circuits.
Ohm’s Law
Ohm’s Law is a relationship between the ratio of voltage and current
to the resistance of a circuit. The law states that a voltage of 1 volt
will create a current of 1 ampere in a circuit having a resistance of 1
Ohm. Ohm’s Law can be expressed as follows:
where E or V = Voltage (electromotive force)
I = Current (amperes)
R = Resistance (Ohms)
E or V = IR
I = E/R
R = E/I
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