Kirchhoff's Rules and terminal voltage

  • Thread starter Thread starter Kandycat
  • Start date Start date
  • Tags Tags
    Rules Voltage
AI Thread Summary
The discussion focuses on applying Kirchhoff's rules to determine the currents (I1, I2, I3) in a circuit with internal resistance of batteries. Participants clarify that the sum of currents entering a junction equals the sum of currents leaving (I1 = I2 + I3). The internal resistance affects the terminal voltage of the 6.0 V battery, which is calculated as 6V plus the voltage drop due to internal resistance (I3*r). Participants emphasize the importance of writing loop equations for accurate calculations and confirm that only two inner loops are necessary for solving the problem. Terminal voltage is ultimately expressed as 6V + I3*r, depending on the current direction.
Kandycat
Messages
21
Reaction score
0

Homework Statement


(a) Determine the currents I1, I2, I3 in the figure. Assume the internal resistance of each batter is r = 1.0 olms

(b) What is the terminal voltage of the 6.0 V battery?


24p9pio.jpg


I hope you can read my handwriting.

Homework Equations


V = IR


The Attempt at a Solution


I1 + I2 = I3

I don't understand kirchhoff's rules and how the internal resistance of each batter means.
 
Physics news on Phys.org
First the way it's drawn it's I2 + I3 = I1

All it means is that charge has to go somewhere. ∑ I_in = ∑ I_out

Direction matters.

The little r's are the internal resistances of the batteries. When they ask for the terminal V of the 6v battery they want you to include the I3*r change in voltage from 6v that you would measure in real life.

To solve you need to write out the loop equations for the 2 inner loops. Those along with your current conservation give you 3 equations and you have 3 unknown currents. So then you just solve.
 
1szfdd.jpg


Okay, can you tell me if my loops are right?

Top: V1 + V2 = I1r + I1R1 + I2r + I2R2 + I1R3

Bottom: V3 + I2R2 + I2r = I1r + I3r + I3R5 + V2 + I3R4

Big: V1 + V3 = I1r + I1R1 + I3R4 + I3r + I3R5 + I1R4
 
First of all forget the Big loop. The 2 inner loops and the conservation of current is all you need.

The top and bottom look OK just glancing at them.

Now use

I1 = I2 + I3 and you can get it down to 2 equations and 2 unknowns pretty pronto.

Then solve.
 
Okay, so I figure out the currents. I'm still pretty confused with finding terminal voltage.

Are you saying that Terminal Voltage = I3r?
 
Kandycat said:
Okay, so I figure out the currents. I'm still pretty confused with finding terminal voltage.

Are you saying that Terminal Voltage = I3r?

No. Terminal voltage is 6v + I3*r. (This is if that is the right direction for I3.)
 
Thread 'Voltmeter readings for this circuit with switches'
TL;DR Summary: I would like to know the voltmeter readings on the two resistors separately in the picture in the following cases , When one of the keys is closed When both of them are opened (Knowing that the battery has negligible internal resistance) My thoughts for the first case , one of them must be 12 volt while the other is 0 The second case we'll I think both voltmeter readings should be 12 volt since they are both parallel to the battery and they involve the key within what the...
Thread 'Struggling to make relation between elastic force and height'
Hello guys this is what I tried so far. I used the UTS to calculate the force it needs when the rope tears. My idea was to make a relationship/ function that would give me the force depending on height. Yeah i couldnt find a way to solve it. I also thought about how I could use hooks law (how it was given to me in my script) with the thought of instead of having two part of a rope id have one singular rope from the middle to the top where I could find the difference in height. But the...
Back
Top