Understand a little, You don’t have to worry about Lifetime Kirchhoff’s formula. I hope so. Before discussing Kirchhoff’s formula, let me briefly say a few things.
Suppose a road is sloping from north to south. That means the road is high on the north and low on the south. Now if you want to cycle from north to south, the road will support you. But if you want to go north from the south side of the road, the road will block you. The road will take as much extra strength from you as it did before. Batteries play such a role in circuits. As we know, the battery in the circuit always supplies power. But this is not true in all cases. If you move a battery from minus to plus or pass the battery from minus to plus, the battery will give you a voltage equal to its written voltage. Much like cycling from north to south.
Again, if you go in the opposite direction or pass the battery from plus to minus, the battery will take a voltage equal to the voltage written on it. Just like what happened to cycling from south to north.
And for that we will say, the direction of voltage or electromagnetic power of the battery when passing the battery from minus to plus. That is, the circuit will turn from the plus end of the battery to enter minus.
Now I will talk about prevention.
Resistance is like a broken bridge. No matter which way you cross the broken bridge, it will stop you. In the same way, if the resistance can be crossed from the front or the back, it will be blocked in both cases. So we will always give a negative mark in front of the resistor voltage. Again, there is a direction to the current that flows through the resistor. The circuit may contain one or more batteries. But whichever battery you choose (whatever you want) will be the direction of the voltage of the battery, the direction of the current in the whole circuit, and of course the direction.
With these words in mind, Kirchhoff’s formula will become as straightforward as water for you. How? Showing. Listen to the formula once before. The formula is – the sum of the total voltages in a closed loop of the circuit will be zero.
Now where is the story of this voltage? In batteries and in resistors. Somewhere rise, somewhere fall. She will read the story. And there is resistance. So that the voltage always drops. Now one thing to keep in mind when formulating a cursor is that if a vector goes in the opposite direction to the sign, there is a minus sign in front of it. (What’s that? The kids know it too !!!)
Now if you have a battery in the circuit, it will be, and if you have more than one battery, the current will flow in the whole circuit according to its vector direction (i.e. the circuit turns from the plus edge to the minus). Accordingly, draw an arrow pointing at the current in the circuit. The work is done. Now add the voltage (E or V) of all the batteries and subtract the resistance voltage (IR) and give equal zero. However, since E, V and I are vector numbers, don’t forget to put the appropriate mark (plus or minus) in the first parentheses in front of them. Now draw and solve the desired circuit. To those of you who understand every word of mine, it may seem like-is Kershaw’s formula so simple? Okay, so let’s solve a circuit.
Since there are multiple batteries in the circuit in the figure, we consider the E1 battery to be the main battery. Its flow direction is from minus to plus. According to this direction, I took the directional sign of electric current in the whole circuit. Then the direction of electric current in the whole circuit is towards the arrow pointing towards us. Since the whole circuit is in series, so the value of current flowing through all batteries and resistors is equal and I am denoting it by I.
Now our job is to add the battery voltage and subtract the resistor voltage to give equal zero.
E1 – IR1 + (-E2) – IR2 + E3 – IR3 = 0
Everything was fine. But we put a negative sign in front of E2, because its direction is the opposite of our indicated direction, which we have already explained with the example of a sloping road.
Now if we apply our formula in the opposite direction to our direction, then-
(-E1) – (-I) .R3 + E3 – (-I) .R2 + (-E2) – (-I) .R1 = 0
Similarly we put negative marks in front of E1 and E3, because its direction is opposite to ours this time. There is a negative sign in front of electric current I. Because its direction is directed towards us, but we are going in the opposite direction. Now draw the desired circuit and practice.
Happy circuit.
Jeion Ahmed
EEE CUET
