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