Key Fact
Resistors
In parallel circuit, total resistance can
be found from
1 1
T 3
R
Example 1
Three resistors are connected (a) series (see Fig. Craft
students need only state the expression 1/RT 1/R1 1/R2 1/R3 for par-
allel connections.4
Resistors parallel.
R1 Ω
V1
R2 Ω
V2
VT 12V
V3
FIGURE 5.4) into equation (5. 5. 5.3
Resistors series.3) have:
I I
T 3
∴
V
R
V
R
V
R
V
R
T
Now, since common all terms the equation, can divide both
sides leaving with expression for the circuit resistance:
1 1
T 3
R
Note that the derivation this formula given for information only.4),
across 12V battery. For each method connection, find the total resistance and the values
of all currents and voltages.
.Basic scientific concepts electrotechnology
105
We are looking for expression for the equivalent resistance any paral-
lel circuit and, substitute equations (5.3), and (b) parallel (see Fig.
R1 Ω
R2 Ω
R3 Ω
IT
I1
I2
I3
VT 12V
FIGURE 5
