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.)
 
TL;DR Summary: I came across this question from a Sri Lankan A-level textbook. Question - An ice cube with a length of 10 cm is immersed in water at 0 °C. An observer observes the ice cube from the water, and it seems to be 7.75 cm long. If the refractive index of water is 4/3, find the height of the ice cube immersed in the water. I could not understand how the apparent height of the ice cube in the water depends on the height of the ice cube immersed in the water. Does anyone have an...
Kindly see the attached pdf. My attempt to solve it, is in it. I'm wondering if my solution is right. My idea is this: At any point of time, the ball may be assumed to be at an incline which is at an angle of θ(kindly see both the pics in the pdf file). The value of θ will continuously change and so will the value of friction. I'm not able to figure out, why my solution is wrong, if it is wrong .
Back
Top