Environmental Engineering Reference
In-Depth Information
By Ohm's law, the current is
E
R
T
100
70
I
===
143
.
mperes
The voltage (
E
1
) across
R
1
is
E
1
=
I
×
R
1
= 1.43 amperes × 20 ohms = 28.6 volts
The voltage (
E
2
) across
R
2
is
E
2
=
I
×
R
2
= 1.43 amperes × 20 ohms = 28.6 volts
The voltage (
E
3
) across
R
3
is
E
3
=
I
×
R
2
= 1.43 amperes × 30 ohms = 42.9 volts
The power dissipated by
R
1
is
P
1
=
E
1
×
I
= 28.6 volts × 1.43 amperes = 40.9 watts
The power dissipated by
R
2
is
P
2
=
E
2
×
I
= 28.6 volts × 1.43 amperes = 40.9 watts
The power dissipated by
R
3
is
P
3
=
E
3
×
I
= 42.9 volts × 1.43 amperes = 61.3 watts
The total power dissipated is
P
T
=
E
T
×
I
= 100 volts × 1.43 amperes = 143 watts
Note:
Keep in mind when applying Ohm's law to a series circuit to consider
whether the values used are component values or total values. When the informa-
tion available allows the use of Ohm's law to find total resistance, total voltage,
and total current, then total values must be inserted into the formula.
To find total resistance:
E
I
T
T
R
=
T
To find total voltage:
E
T
=
I
T
×
R
T
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