What is Kirchhoff’s Law?
The Kirchhoff’s law is some similar to Ohms law
but it describe some rules of current and voltage in a circuit.
Basically we have two types of circuit which is
- Simple circuit
- Complex circuit
What is difference between these two circuits?
1- Simple Circuit
The circuit has only one power source and many
resistances, it called normal circuit.
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| Simple circuit |
You can watch clearly that this circuit has only one power source, and two resistances, resistance denoted to load, in this circuit power source will remain one and Resistance can be one or more above such as 2, 3, 9, and so 'on.
2- Complex Circuit
The which circuit power source has more than
One, it called Complex circuit
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| Complex Circuit |
In this types of circuit power source always
will be more than one, such 2,5,8 and so ‘on, but it Resistance can be one or
more, in simple words this circuit will has more than one power source.
So, we can easily use Ohms law in the normal
circuit, but ohms law can't apply at Complex circuit, for this Kirchhoff’s law
use for Complex circuit’s for calculation.
There are two Kirchhoff’s Law or Rule
- Current Law/Rule
- Voltage Law/Rule
The Kirchhoff first rule says that the sum of
all currents at a point in a circuit will be zero.
And the much amount of Current enters the circuit;
the same amount of current will go out from the circuit.
Example:-
We have a circuit with four resistances, and all
four resistance meet at a common point and it make forms of a junction.
We have supplied 4 amps current at point 1,
and 5 amps current supplied at point 2, such sum of these two currents
is equal to 9 amp, now same 9 amps current will out from point 3
and point 4.
The sum of outgoing current will be equal to 9,
it will not be change, means it not will 7-8.
But it can divide into different amount, because
it has two paths for outgoing, it possible that 7 amps out from point 3
and, and remaining 2 amps current out from point 4, and vice versa,
means outgoing current can be divide into different amount, but it not be less.
Also this possible that we have two input paths
and three output paths, so if 10 amps current come from two input path, now it
will out from three paths, so it can be divide in three amounts.
The Kirchhoff’s second rules says that sum of all potential changes in a closed circuit will equal to zero.
Example
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| Loop circuit |
This is a loop or closed Circuit, when we sum all values of these, so we will get zero.
How to write equation?
When current go to negative from Positive then current will be zero, and when current go to positive from negative then current be positive, this is most important rules of Kirchhoff's law for remembering, if we do mistake in it, then equation will be wrong and answer will come wrong.
For this when we make equation of any Circuit, so we first need to select that how we take values, such as first we needs to identify current direction.
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| current direction |
This is the circuit we will equation.
So now we take current direction in Clock wise, this is not matter that how we take current direction, also we current direction take like anti Clock wise, or Clock wise, this remember that which direction we selected first time, then we apply same direction in whole circuit.
If we selected current direction first time in Clock wise than we can't change into anti close wise, if we do change, then equation will wrong.
Example:- We have assumed current direction in Clock wise, then we takes values like clockwise.
Now make equation
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| Kirchhoff's law |
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