Kirchhoff’s Current Law; Kirchhoff’s Voltage Law - Cub Cadet 6X4 Shop Handbook

5. Kirchhoff's current law:
• Kirchhoff's current law deals with nodes. Nodes
are the junction of two or more wires or the junc-
tion of a wire to a component.
• Kirchhoff's current law states that what ever cur-
rent goes into a node must come out.
• As an example: Three wires are connected with
a wire nut. One wire has 5 amps going into the
connection.
The sum of the current coming out of the other
two wires must equal 5 amps. That could be 3
amps in one wire and 2 amps in the other or it
could be 2.5 amps in each wire, but the total
coming out must be the same as the current
going in. See Figure 9.45.
Node
5 Amps
Figure 9.45
3 Amps
2 Amps
6. Kirchhoff's voltage law:
• Kirchhoff's voltage law deals with voltage drops.
A voltage drop is the amount of voltage used up
or "dropped" by resistance in a circuit. Ohm's law
states that V = IxR, every component in a circuit
has resistance, even the wires.
To push current through resistance, it takes volt-
age. Kirchhoff's voltage law states that the sum
of all the voltage drops equals the source volt-
age.
• As an example, imagine a circuit that has a 12V
battery that produces 4 amps of current power-
ing a light bulb that creates 3 Ω of resistance.
The wires are assumed to have 0 Ω resis-
tance*.
The light bulb uses 12 volts (4 amps x 3 ohms =
12 volts).
The battery produces 12 volts that equal the 12
volts used by the light bulb. See Figure 9.46.
12 Volts
4 Amps
NOTE: * If the proper size wire is used and
there is no corrosion in the wire, the resistance
will be too small to worry about.
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Chapter 9 - Electrical
4 Amps flow
X
3 Ω resistance
=
12 Volts
Figure 9.46