Chapter 33

A $10\mathrm{m}$ wire potentiometer is connected to an accumulator of steady voltage. A $7.8\mathrm{m}$ length of it balances the emf of a cell on 'open- circuit'. When cell delivers current through a conductor of resistance $10\mathrm{\Omega }$ it is balanced against $7.0\mathrm{m}$ of the same potentiometer. What is the internal resistance of the cell ? (A) $1.24\mathrm{\Omega }$ (B) $1.36\mathrm{\Omega }$ (C) $1.14\mathrm{\Omega }$ (D) $1\mathrm{\Omega }$

A potentiometer is preferred over a voltmeter to measure the emf of a cell because... (A) The material of the potentiometer wire has a low temperature coefficient of resistance. (B) emf measured by potentiometer is more accurate because the cell is open- circuit. (C) potential gradients can be varied in a potentiometer using a rheostat. (D) Potentiometer is more sensitive than voltmeter.

In the experiment of potentiometer wire $\mathrm{AB}$ is $100\mathrm{cm}$ long shown in figure When $\mathrm{AC}=40\mathrm{cm}$, no deflection occurs in the galvanometer. What is the value of $R$ ? (A) $15\mathrm{\Omega }$ (B) $18\mathrm{\Omega }$ (C) $12\mathrm{\Omega }$ (D) $14\mathrm{\Omega }$

In experiment of the potentiometer wire $\mathrm{AB}$ of length $100\mathrm{cm}$ has a resistance of $10\mathrm{\Omega }$. It is connected in series with a resistance $\mathrm{R}$ and a cell of emf 2 volts and of negligible internal resistance. A source emf $10\mathrm{mV}$ is balanced against a length of $40\mathrm{cm}$ of the potentiometer wire. What is the value of the external resistance? (A) $900\mathrm{\Omega }$ (B) $820\mathrm{\Omega }$ (C) $790\mathrm{\Omega }$ (D) $670\mathrm{\Omega }$

A potentiometer wire, which is $4\mathrm{m}$ long is connected to the terminals of a battery of steady voltage. A leclanche cell gives a null point at $1\mathrm{m}$ if the length of the potentiometer wire be increased by $1\mathrm{m}$, What is the new position of the null point? (A) $1.25\mathrm{m}$ (B) $1.4\mathrm{m}$ (C) $1.75\mathrm{m}$ (D) $1.2\mathrm{m}$

A battery of $2\mathrm{V}$ and internal resistance 1 is used to send a current through a potentiometer wire of length $200\mathrm{cm}$ and resistance $4\mathrm{Q}$ What is the potential gradient of the wire? (A) $8\times {10}^{-3}\mathrm{V}{\mathrm{cm}}^{-1}$ (B) $4\times {10}^{-3}\mathrm{V}{\mathrm{cm}}^{-1}$ (C) $6\times {10}^{-3}\mathrm{V}{\mathrm{cm}}^{-1}$ (D) $2\times {10}^{-3}\mathrm{V}{\mathrm{cm}}^{-1}$