Environmental Engineering Reference
In-Depth Information
Given:
R
1
= 10 ohms
R
2
= 20 ohms
R
3
= 40 ohms
I
= 2.5 amperes
Because the circuit involved is a series circuit, the same 2.5 amperes of current
flow through each resistor. Using Ohm's law, the voltage drops across each of the
three resistors can be calculated:
E
1
= 25 volts
E
2
= 50 volts
E
3
= 100 volts
When the individual drops are known, they can be added to find the total or
applied voltage by using Equation 10.9:
E
T
=
E
1
+
E
2
+
E
3
E
T
= 25 V + 50 V + 100 V = 175 V
Note:
The total voltage (
E
T
) across a series circuit is equal to the sum of the volt-
ages across each resistance of the circuit.
Note:
The voltage drops that occur in a series circuit are in direct proportion to
the resistance across which they appear. This is the result of having the same cur-
rent flow through each resistor. Thus, the larger the resistor, the larger will be the
voltage drop across it.
s
eries
C
irCuit
p
oWer
Each resistor in a series circuit consumes power. This power is dissipated in the form
of heat. Because this power must come from the source, the total power must be
equal in amount to the power consumed by the circuit resistances. In a series circuit,
the total power is equal to the sum of the powers dissipated by the individual resis-
tors. Total power (
P
T
) is thus equal to
P
T
=
P
1
+
P
2
+
P
3
+ … +
P
n
(10.10)
where
P
T
= Total power (W).
P
1
= Power used in first part (W).
P
2
= Power used in second part (W).
P
3
= Power used in third part (W).
P
n
= Power used in
n
th part (W).
Search WWH ::
Custom Search