Understanding Electromotive Force and Internal Resistance in Batteries

In summary, when calculating the electromotive force, it is important to open the switch and use a voltmeter to measure the exact voltage of the battery. When the switch is closed, there will be a voltage drop due to the current and internal resistance of the battery. However, it is unclear if the same applies to reading the voltage when the circuit is complete. Additionally, it is important to use a multimeter with high input impedance and a potentiometer circuit to measure the emf accurately without drawing too much current from the battery.
  • #1
yuganes warman
uploadfromtaptalk1426328363255.png

sorry for the drawing.Hope you guys can bear with it.
The electromotive force can be calculated by opening the switch and the voltmeter will show the exact voltage of the battery. When the switch is closed,there will be a voltage drop due to the internal resistance of the battery. The question is, there will be a potential different across the two points between the battery when the circuit is incomplete which will show the exact voltage of the battery,but does the same goes to reading of the voltage given that the circuit is complete ? Why ? (please refer to the drawing)
another question, if there is an internal resistance within the battery why do they requirre the two points ? and why not just connect the voltmeter to the positve and negative terminal of the battery ? Thanks !
 
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  • #2
yuganes warman said:
there will be a voltage drop due to the internal resistance of the battery
More correct: A voltage drop due to the current through the battery and the internal resistance of the battery.
yuganes warman said:
another question, if there is an internal resistance within the battery why do they requirre the two points ? and why not just connect the voltmeter to the positve and negative terminal of the battery ?
The internal resistance is not a resistor, it is due to the construction of the battery. The internal resistance is defined as the drop in battery voltage divide by the current drawn from the battery.
yuganes warman said:
The question is, there will be a potential different across the two points between the battery when the circuit is incomplete which will show the exact voltage of the battery,but does the same goes to reading of the voltage given that the circuit is complete ? Why ?
Sorry, I have no idea what you are asking.
 
  • #3
Best to have a multimeter to measure the respective values before trying to understand the completion of a circuit. Electrons flow from positive to negative between two points upon the closing of a circuit. <link deleted>
 
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  • #4
To measure the emf of a voltage source you must not draw any current (or very little current) from the voltage source during the measurement. When using a voltmeter use one with a high input impedance ( resistance) usually rated by the number of ohms per volt measured. Best above 1 megaohm per volt. For the best accuracy use the potentiometer circuit below the accuracy of which is only limited by the accuracy of the standard cell and the ratio of the resistance arrived at in its adjustment.

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1. What is electromotive force (EMF) in a battery?

Electromotive force, also known as voltage, is the measure of the energy per unit charge that is supplied by a battery. It is the driving force that causes charge to flow through a circuit.

2. What is internal resistance in a battery?

Internal resistance in a battery is the resistance to the flow of electric current within the battery itself. It is caused by the resistance of the materials used to make the battery, such as the electrolyte and electrodes. This resistance can reduce the overall voltage output of the battery.

3. How does internal resistance affect the performance of a battery?

The internal resistance of a battery can cause a decrease in the voltage output and energy efficiency of the battery. This results in a shorter lifespan and reduced capacity of the battery. Internal resistance can also lead to heating of the battery, potentially causing damage or even explosion.

4. How can the internal resistance of a battery be measured?

The internal resistance of a battery can be measured by using a multimeter or battery analyzer. The device measures the voltage output of the battery under load and calculates the internal resistance using Ohm's law (R = V/I).

5. How can the internal resistance of a battery be reduced?

The internal resistance of a battery can be reduced by using materials with lower resistance in the construction of the battery, such as using thicker electrodes or a more conductive electrolyte. Proper maintenance and avoiding extreme temperatures can also help reduce internal resistance and improve battery performance.

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