Understanding Kirchhoff's Voltage Law in Circuit Analysis

In summary, Kirchhoff voltage law can be used to find the current through a battery from point A to point B. The current will be smaller than 1 A if the voltage across the battery is 2 volts or less.
  • #1
luysion
35
0
Hello.
The question appears not to complex! however I am been on break (and still am haha) but I saw this in an old exam paper and its bugging me that I don't know how to do it!

heres the question;
http://img59.imageshack.us/img59/9868/dfdfmu.jpg

Kirchhoff voltage law comes to mind. However I am confusing myself. I thought that the current across each resistor in one of the closed loops can't be the same? or can it?
anywhos ignore my little rant. Id really appreciate if somone could explain to me the answer cheers.
 
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  • #2
Is there a way to simplify the circuit to find the current from the battery? Look at how the resistors are arranged.
 
  • #3
I am new to this as well in my circuits class, so anyone correct me If I am wrong.
At point A the voltage from the battery hasn't reached any electrical resistance yet, correct?
So would not the voltage be the same since as it started 2 volts because it hasn't reached resistors yet?
And solving for current would be just doing a little algebraic manipulation of one form of the equation for voltage

[itex]V=IR[/itex] and resolving to find current [itex]I=\frac{V}{R}[/itex]

?

I think I might be way off... :(
 
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  • #4
Start from the right of the circuit. There are some resistors in series.

What would be the size of one resistor that could replace these three resistors?

[URL]http://upload.wikimedia.org/math/0/1/5/01541fd01585b4f8ba5ac819e4abc042.png[/URL]


Then, take this new resistor and put it in parallel with the 4 ohm resistor. What is the formula for two resistors in parallel?
dc55458c0154c67e7e8eed2b2e5b835a.png



So, you could put one resistor in here that is equivalent to the 4 resistors.


Now, you have 3 resistors in series. How do you get the equivalent resistance of these 3 resistors?
[URL]http://upload.wikimedia.org/math/0/1/5/01541fd01585b4f8ba5ac819e4abc042.png[/URL]

So, now there is one resistor across a battery. Ohms Law tells you what the current will be.
7564ef88e7c926febabebd837d9f744a.png
 
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  • #5
hey i think u should use mesh analysis for solving this circuuit. consider separate currents I1 and I2 for the two loops.now apply kirchhoffs voltage law in both the loops sepreately.solve for I1 and I2.
the value of I1 will give u the current at point A.
 
  • #6
No real need to calculate. The current has to pass the two 1 Ohm resistors on the left, and then at least one more resistor. Hence, the resistance is larger than 2 Ohms, this means the current must be smaller than 2V/2Ohm = 1 A. I only see one answer smaller than one.
 
  • #7
It should be mental arithmetic anyway.

1 + 2 + 1 = 4

4 // 4 = 2

1 + 2 + 1 = 4

2 / 4 = 0.5
 
  • #8
hey sorry late reply guys, thanks so much for the help :)
 

FAQ: Understanding Kirchhoff's Voltage Law in Circuit Analysis

What is a circuit in physics?

A circuit in physics refers to a closed path or loop through which an electric current can flow. It is made up of various components such as resistors, capacitors, and inductors, connected by conductive wires.

What is the difference between series and parallel circuits?

A series circuit is one in which all components are connected in a single loop, while a parallel circuit has multiple branches where components are connected. In series circuits, the current remains constant throughout, while in parallel circuits, the voltage remains constant.

How do I calculate the total resistance in a series circuit?

To calculate the total resistance in a series circuit, you simply add up the individual resistances of each component. The formula for calculating total resistance in a series circuit is R = R1 + R2 + R3 + ... + Rn, where R is the total resistance and R1, R2, R3, etc. are the resistances of each component.

How do I calculate the total resistance in a parallel circuit?

Calculating the total resistance in a parallel circuit is a bit more complicated. You first need to find the reciprocal of each component's resistance, add these reciprocals together, and then take the reciprocal of that sum. The formula for calculating total resistance in a parallel circuit is 1/R = 1/R1 + 1/R2 + 1/R3 + ... + 1/Rn, where R is the total resistance and R1, R2, R3, etc. are the resistances of each component.

What is Kirchhoff's Circuit Laws?

Kirchhoff's Circuit Laws, named after German physicist Gustav Kirchhoff, are two fundamental laws that govern the behavior of electric circuits. The first law, also known as Kirchhoff's Current Law (KCL), states that the sum of the currents entering a junction or node in a circuit must equal the sum of the currents leaving that junction. The second law, also known as Kirchhoff's Voltage Law (KVL), states that the sum of the voltage drops in a closed loop must equal the sum of the voltage sources in that loop.

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