Question

Potentiometer wire Pq of length 1m is connected to a standard cell $E_1$ Another cell of E2 of emf1.02v/s connected as shown in the circuit diagram with a resistance 'r' and with a switch 's' . With the switch S open, null position is obtained at a distance of 51 cm from p,Calculate

• A. Potential gradient of the wire.
• B. emf of the cell.
• C. When switch S is closed, will null point moves towards p or Q?
• D. insufficient data
  

Answer 1

The correct option is C When switch S is closed, will null point moves towards p or Q?

Length of potentiometer wire $l=1m$

Emf $e=E_1$

Emf of cell $E_2=1.02v/s$

Null point $=51cm=0.51m$

(a)Potential gradient of the wire

$V=\frac{1.02}{0.51}$

$V=2V/m$

(b) Emf of cell

$V_{PQ}=E_1$

$E_1=2V$

(c) When switch S is closed, null point does not shifts because current if not drawn from E₂ again.