For each method connection, find the total resistance and the values
of all currents and voltages.
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.
R1 Ω
R2 Ω
R3 Ω
IT
I1
I2
I3
VT 12V
FIGURE 5.4
Resistors parallel.
. Craft
students need only state the expression 1/RT 1/R1 1/R2 1/R3 for par-
allel connections.4),
across 12V battery.4) into equation (5. 5. 5.3), and (b) parallel (see Fig.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.Basic scientific concepts electrotechnology
105
We are looking for expression for the equivalent resistance any paral-
lel circuit and, substitute equations (5.
R1 Ω
V1
R2 Ω
V2
VT 12V
V3
FIGURE 5
