What is potentiometer ? Explain principle of potentiometer.

Explanation

`rArr` Potentiometer is a device in which continously varying potential difference can be obtained and measured also.
`rArr` Device measuring potential difference is called potentiometer.
Principle:

`rArr` As shown in figure, a battery having emf t and internal resistance r is connected with resistance box R and wire with uniform cross- section and uniform resistance per unit length (AB) are connected in series.
`rArr` Resistance box (R) is always not needed.
`rArr` length of AB wire = L
`rArr` Let resistance of wire per unit length is `rho` .
`therefore ` Resistance of wire AB = L `rho`
`rArr` Let value of resistance obtained (used) from resistance box is R.
`thereforre ` Current flowing in the wire,
`I = (epsilon)/(R + L rho + r) " " `.... (1)
`rArr ` If length of AC wire is l then, resistance of AC wire = `rho ` l
`rArr` Potential difference between A and C = current `xx ` (resistance of AC )
`therefore V_(l) = epsilon (l) = I rho l " "`....(2)
`rArr therefore epsilon (l) = ((epsilon rho )/(L rho + R + r)) . l `
`therefore epsilon (l) = V = phi `l
Where `phi ` or `sigma ` of K is called potential gradient.
`rArr` Principle : Potential difference between two point of wire is directly proportional to distance between two points.
`rArr` Its unit is `Vm^(-1) ` and
dimensional formula `[M^(1) L^(1) T^(-3) A^(-1) ] `