Current electricity and circuits

In summary, when K1 is closed, the current through R1 is zero, and the current through R2 is also zero.
  • #1
Abhishekdas
208
0
Current electricity...

Homework Statement


In the circuit shown(please refer to attchment) only thing missing is that the battery has an internal resistance of r. Now When key K1 is closed the ammeter reads I0 whether K2 is open or closed. But when K1 is open the ammter reads I0 /2 when K2 is closed. Assuming that ammeter resistance is much less than R2 find R1 and r.
Here R2=100 ohm and R3 = 100 ohm


Homework Equations





The Attempt at a Solution


Now in the diagram no Ammeter is visible ...So i proceeded assuming that ammeter is attached to the main circuit ie anywhere near the battery...Now i don't get this "When key K1 is closed the ammeter reads I0 whether K2 is open or closed"...how can this I0 be independent of R3?
 

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  • #2


Waiting for a reply soon...thank you...
 
  • #3


At first glance, I don't see any place where an ammeter could be placed that would be unaffected by opening and closing K2 while K1 is closed.

When K1 is closed it short-circuits resistor R1. That effectively removes R1 from the circuit, since no potential difference can be developed across it. If you then redraw the circuit for this case (K1 closed), you have what I show in the attached image.

Now, where could you put an ammeter in that circuit such that its reading would be unaffected by K2? The internal resistance of the battery (what I've shown as Ri) will have different voltage drops depending upon whether K2 is open or closed. This will affect currents in all branches. (Perhaps this is telling you something about the value of the internal resistance).
 

Attachments

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  • #4


Ya... i agree with you...So basically it seems there is something wrong with the question isn't it? I guess better off leaving it...Just wanted to confirm that my concepts are fine...

Thank you gneill...
 
  • #5


Abhishekdas said:
Ya... i agree with you...So basically it seems there is something wrong with the question isn't it? I guess better off leaving it...Just wanted to confirm that my concepts are fine...

Thank you gneill...

Suppose that the ammeter were placed in series with R2, and further suppose that Ri and R1 were zero ohms. How would the circuit operation compare against their description?
 
  • #6


This time...the current through current is independent of K2...right...
In the book the answer for internal resistance is as you say 0 but R1 is 50...
But R1 can't be non zero because in such a case the current in ammeter is not independent of k2...Isnt it? So R1 = 0 and Ri being 0 is the only case that makes sense...
 
  • #7


That's what it looks like to me, given your initial drawing.
 

1. What is current electricity?

Current electricity is the flow of electric charge through a conductive material, such as a wire. It is caused by the movement of electrons, which are negatively charged particles, through a closed circuit.

2. What is the difference between AC and DC current?

AC (alternating current) is a type of current that constantly changes direction, while DC (direct current) flows in only one direction. AC is commonly used in household electricity, while DC is used in electronics and batteries.

3. How is current measured?

Current is measured using a device called an ammeter, which is placed in series with the circuit. It measures the amount of current flowing through a specific point in the circuit in units of amperes (A).

4. What is a circuit?

A circuit is a closed loop through which electric charge can flow. It is made up of several components, such as a power source, conductors, switches, and loads, that work together to provide a complete path for current to flow.

5. How do circuits work?

Circuits work by allowing a continuous flow of electric charge from the power source to the load and back to the power source. This flow of charge is facilitated by the conductors in the circuit and can be controlled by switches or resistors, which can alter the amount of current flowing through the circuit.

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