What is the Internal Resistance of a Cell?

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SUMMARY

The internal resistance of a cell can be determined using the voltage readings across the cell in a circuit with a 2 Ohm resistor. When the switch is open, the voltmeter reads 12V, and when closed, it reads 8V. The internal resistance is calculated to be 1 Ohm. This conclusion is reached by analyzing the voltage drops and the constant current in the circuit.

PREREQUISITES
  • Understanding of Ohm's Law (V=IR)
  • Basic knowledge of electrical circuits and components
  • Familiarity with voltage drops in series circuits
  • Concept of internal resistance in batteries or cells
NEXT STEPS
  • Study the concept of internal resistance in batteries and its impact on performance
  • Learn about series and parallel circuits and their voltage characteristics
  • Explore the application of Ohm's Law in real-world electrical problems
  • Investigate methods for measuring internal resistance in various types of cells
USEFUL FOR

This discussion is beneficial for physics students, electrical engineering students, and anyone interested in understanding the behavior of cells in electrical circuits.

huey910
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Homework Statement


A voltmeter is connected across a cell in a circuit containing a switch and a 2Ohm resistor. When the switch is open, the voltmeter reads 12V. When it is closed, the reading is 8V. Find the internal resistance of the cell.


Homework Equations


I tried to use V=IR - is I constant? does this have to do with voltage drops?


The Attempt at a Solution


the solution is 1Ohm. Why is that?
 
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huey910 said:

Homework Statement


A voltmeter is connected across a cell in a circuit containing a switch and a 2Ohm resistor. When the switch is open, the voltmeter reads 12V. When it is closed, the reading is 8V. Find the internal resistance of the cell.


Homework Equations


I tried to use V=IR - is I constant? does this have to do with voltage drops?
You're dealing with a DC source (a cell) and resistances, so yes, the current I is constant.
Yes, this has to do with voltage drops. Can you identify where voltage drops are occurring and what their values are?

The Attempt at a Solution


the solution is 1Ohm. Why is that?
Isn't that what you need to show?

Have you sketched the circuit as described? With the given information, what expressions can you write for current and potential drops? Can you determine any of the values?
 

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