DC CROMPTON POTENTIOMETER PDF SERIES
Galvanometer G is connected in series with a key and multi current switch by which either the standard call on the unknown emf is connected. R1 is for coarse adjustment and R2 is for fine adjustment. Sliding over the slide wire & studes of the resistance coils. It consists of a graduated slide wire Ac which is connected in series with 14 coils, each of which has a resistance exactly equal to that of slide wire.Ģ. The crompton potentiometer Construction: 1. Let the lenth is L2 then B2 = i l2 E1Į1 l1 E2 l2 If E1 is a known emf then E2 can be calculated by measuring the length l1 & l2. Simillarly B1 is replaced by another emf B2 and the contact point C is varied till null deflection of galvanometer. Let length of AC is l 1 then volt drop is il1 it is equal to B1. The sliding contact C is adjusted till no current flows through the galvanometer that implies the volt drop across AC is equal to B1. B1 is a battery whose emf is to be measured G is the DC1 galvanometer B is the battery which supplies current to the slide wire Let is the (resistance / unit length) of slide wire i is the current through the slide wire when key K is open, when the key k is closed a current will flow through the galvanometer if the volt drop across AC slide wire is not equal to B1.
AB is a slide wire of uniform cross section R is a regulating resistance to limit the current (i) through the slide wire. Potentiometers with Direct current: As shown in the fig. The magnitude of the current is adjusted in such a way that the voltage drop across the resistance is equal to 1 volt.Potentiometers Potentiometer is used for the measurement of emfs by comparison with a standard emf. The ammeter is used in the circuit for determining the magnitude of current passing through resistor during the reading. If the magnitude of current remains same, the circuit gives the accurate result. The accuracy of the unknown resistance also depends on the magnitude of the current at the time of the readings. The accuracy of unknown resistance depends on the value of standard resistance. On equating the equation (1) and (2), we get The switch, when moves to position 1, 1 the unknown resistance connects to the circuit, and when it moves to position 2, 2 the standard resistance connects to the circuit.Ĭonsider that when the switch is in position 1,1 the voltage drop across the unknown resistance is V rĪnd when it is in 2, 2 the voltage drop across the resistance is V s The double pole double throw switch is used in the circuit.
The rheostat is used for controlling the magnitude of current into the circuit. The S is the standard resistance from which the value of unknown resistance is compared. The R is the unknown resistance whose value is needed to be measured. Let understand this with the help of the circuit diagram.
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