Potential difference and terminal potential difference

In summary, the difference between IR and terminal potential difference is that IR takes into account the contact resistance between the resistor and the current carrying leads, while terminal potential difference measures the potential difference across the resistor alone. To get an accurate measurement of the true PD, the voltmeter probe should be placed directly on the resistor ends after the power terminals. If there is no contact resistance or supply lead resistance, then IR and terminal potential difference are the same.
  • #1
patep022
5
0
I really need to know the difference between the two as I have an exam tomorrow D:. What is the difference between the two and how do I calculate each one of them? The book says " IR is the potential difference that is measured across the load resistor R. This is the same as the potential difference that would be measured by a voltmeter connected across the terminals of the supply and is referred to as the terminal potential difference. Termina pd = EMF - Ir"
I = Current
R= Resistance
r= internal resistance
Can someone please word it better or help me out here?
Thank you
 
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  • #2
I was not sure what you were talking about at first but I think you may be referring to the problem of making measurement where there are heavy currents involved. The actual contact resistance (Rc) between the resistor under test and the current carrying leads can cause a voltage drop of IRc. To get an accurate measurement of the true PD across the resistor, you need to put your voltmeter probe right on the resistor ends, after the power terminals. The voltmeter will then be measuring the PD across the resistor alone. Of course, the same current is flowing round the whole circuit so you have a good value I and a good value of Vr and you can calculate the resistor value without the contact resistance.
Could that be what you are worrying about?
If there is no contact resistance or supply lead resistance then the two terms in the title are the same.
 

1. What is potential difference?

Potential difference is the difference in electric potential between two points in an electric circuit. It is measured in volts (V) and represents the amount of energy that is required to move a unit charge from one point to another.

2. How is potential difference different from voltage?

Potential difference is often used interchangeably with voltage, but they are not exactly the same. Voltage is a measurement of the electric potential difference between two points, while potential difference is the actual numerical value of that difference.

3. What is terminal potential difference?

Terminal potential difference (TPD) is the potential difference between the positive and negative terminals of a power source, such as a battery. It represents the amount of energy that the power source can provide to the circuit.

4. What factors affect potential difference?

Potential difference is affected by the type of power source, the resistance of the circuit, and the distance between two points in the circuit. It is also affected by the amount of charge that is being moved and the direction of the current flow.

5. How is potential difference measured?

Potential difference is measured using a voltmeter, which is a device that is connected in parallel to the circuit and measures the difference in electric potential between two points. The voltmeter measures the potential difference in volts (V).

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