ii) potentiometer

PotentiometerPotentiometer is an instrument used for measurement of an unknown emf.

Two Types: DC Potentiometer and AC Potentiometer

Basic Potentiometer:

What do you mean by standardisation of a potentiometer?

To fixed the “working current”.

Standard Cell: Western Normal Cell: 1.0186 V

Laboratory (Crompton’s) type Potentiometer:

Multi-Range Potentiometer:

m

m

m

m

RRRRRR

RRRRRR

+++

=+++

21

21

21

21 )()(mRR =1

m

acm R

EI =2

'

RREI

m

acm +=

2

1.0RR

EIm

acm += mRR 92 =

Ω== 1601 mRR Ω== 144092 mRR

Vernier Potentiometer:

Range: 10μV to 1μV

Standard Cell Dial:

True Zero:

Application of DC Potentiometer:1. Calibration of Voltmeter:

2. Calibration of Ammeter:

3. Measurement of Resistance:

4. Measurement of Power:

5. Calibration of Wattmeter:

Phantom Loading

AC Potentiometer:

Polar Potentiometer: Drysdale

Co-ordinate Potentiometer: Gall Tinsley

A basic condition for balance in an ac potentiometer is the equality ofvoltages under comparison at all instants and it requires equality inphase as well as in magnitude of both the ac sources at every instant.

Standardizing of AC Potentiometer and use of Transfer Instruments

Drysdale AC Polar Potentiometer:

Drysdale AC Polar Potentiometer:

Gall Tinsley AC Potentiometer: