Advertisements
Advertisements
प्रश्न
Write the principle of working of a potentiometer. Describe briefly, with the help of a circuit diagram, how a potentiometer is used to determine the internal resistance of a given cell.
Advertisements
उत्तर
The working principle of a potentiometer is based on Kirchhoff’s voltage law. According to this rule, the algebraic sum of changes in voltage around any closed loop involving resistors and cells in the loop is zero.
Let Φ be the potential drop per unit length in the potentiometer wire.
When only a cell is connected, the balance point is N1.
Appling Kirchhoff’s voltage law,
ε = Φ l1 [l1 = Length at which the balance point is achieved]
When some current is drawn using the resistance box, the balance point is achieved at N2.
V = Φl2
This gives,
`epsi/V = l_1 / l_2`
ε = I (r + R) [R = Resistance of the resistance box]
V = IR
This gives,
`epsi /V = (r+R)/R`
`r = R (l_1/l_2 - 1)`
The internal resistance of the cell can be determined by plugging-in the measured values of l1 and l2.
APPEARS IN
संबंधित प्रश्न
State the principle of working of a potentiometer.
State the principle of a potentiometer. Define potential gradient. Obtain an expression for potential gradient in terms of resistivity of the potentiometer wire.
A battery of emf 4 volt and internal resistance 1 Ω is connected in parallel with another battery of emf 1 V and internal resistance 1 Ω (with their like poles connected together). The combination is used to send current through an external resistance of 2 Ω. Calculate the current through the external resistance.
When the null point is obtained in the potentiometer, the current is drawn from the ______
Two cells when connected in series are balanced on 8 m on a potentiometer. If the cells are connected with polarities of one of the cell reversed, they balance on 2 m. The ratio of e.m.f's of the two cells is ____________.
If the length of potentiometer wire is increased, then the length of the previously obtained balance point will ______.
A potentiometer wire of length 'L' and a resistance 'r' are connected in series with a battery of E.M.F. 'E0' and a resistance 'r1'. A cell of unknown E.M.F, 'E' is balanced at a length 'ℓ' of the potentiometer wire. The unknown E.M.F. E is given by ______
AB is a wire of potentiometer with the increase in value of resistance R, the shift in the balance point J will be:
In an experiment with a potentiometer, VB = 10V. R is adjusted to be 50Ω (Figure). A student wanting to measure voltage E1 of a battery (approx. 8V) finds no null point possible. He then diminishes R to 10Ω and is able to locate the null point on the last (4th) segment of the potentiometer. Find the resistance of the potentiometer wire and potential drop per unit length across the wire in the second case.
What will a voltmeter of resistance 200 Ω read when connected across a cell of emf 2 V and internal resistance 2 Ω?
