How a potentiometer can be used to measure emf of cell?
A potentiometer is an instrument for measuring voltage or ‘potential difference’ by comparison of an unknown voltage with a known reference voltage. Potentiometer is a device used to measure the emf of the cell, potential difference across two terminals, unknown resistance, and internal resistance of the cell.
What is the role of potentiometer in thermocouple experiment?
Thermocouple potentiometer Potentiometers for use with thermocouples also measure the temperature at which the thermocouple wires are connected, so that cold-junction compensation may be applied to correct the apparent measured EMF to the standard cold-junction temperature of 0 degrees C.
How can you produce an emf from the heating of one junction of a thermocouple?
Basically, a thermocouple is a closed circuit formed of two dissimilar metallic conductors to produce an electromotive force (EMF) or voltage. The voltage causes a current to flow when heat is applied to one of the junctions. The current will continue to flow as long as the two junctions are at different temperatures.
Why do we use potentiometer for measuring emf?
The potentiometer is preferred over voltmeter when there is a measurement of emf of the cell because the potentiometer does not draw any current as it is a null device. This is the reason why potentiometer is preferred over voltmeter in order to get the actual measurement of emf.
Which technique is used to measure the emf?
Potentiometry is used to measure emf.
Why do we prefer potentiometer over voltmeter for measuring emf?
The potentiometer is preferred over voltmeter when there is a measurement of emf of the cell because the potentiometer does not draw any current as it is a null device. Whereas voltmeter draws current from the cell.
How does a thermocouple produce an emf?
A popular notion is that the EMF (Electric and Magnetic Fields) is generated at the tip or hot end of the thermocouple at the junction between the two metals. The total EMF generated in a thermocouple is the difference between the EMF’s in both legs. This is due to the Seebeck coefficient of the metal or alloy used.
How thermo emf is generated in thermocouple?
When one of the junctions is kept hot (P) and the other cold (Q) , a current begins to flow from Cu to Fe via the hot junction and from Fe to Cu via the cold junction. A temperature difference of 100oC between the two junctions produces a thermo emf of 0.0013 V in the Cu-Fe thermocouple.
What is potentiometer would you prefer a voltmeter or a potentiometer to measure the emf of a battery?
A potentiometer is preferred to measure the emf of a battery, as it gives a more accurate result. This is because a potentiometer uses the null method to measure emf and it hardly draws any current from the primary circuit.
How do you measure the amount of EMF generated by a thermocouple?
The amount of emf developed within the thermocouple circuit is very small, usually in millivolts, therefore highly sensitive instruments should be used for measuring the emf generated in the thermocouple circuit. Two devices used commonly are the ordinary galvanometer and voltage balancing potentiometer.
How to determine the emf of a cell using a potentiometer?
Using a potentiometer, we can determine the emf of a cell by balancing the length. Here the fall of the potentiometer along the length of the potentiometer wire is equal to the emf of the cell.
How does a potentiometer work?
Potentiometer works on the principle that when a constant current flows through a wire of uniform cross sectional area, potential difference between its two points is directly proportional to the length of the wire between the two points. Using a potentiometer, we can determine the emf of a cell by balancing the length.
Which potentiometer is used in thermocouple circuit?
Two devices used commonly are the ordinary galvanometer and voltage balancing potentiometer. Of those two, a manually or automatically balancing potentiometer is used most often. Figure 2 shows the potentiometer connected in the thermocouple circuit.