A potentiometer wire is of length 10 m and has a total resistance of 18 ohm. It carries a current of 120 mA. What length of it will be necessary to balance a cell of emf 1.5 volt ?

A battery of e.m.f 2V and internal resistance 1Omega is used to send a current through a potentiometer wire of length 200cm and resistance 4Omega . What length of the wire will be required to balance a cell of e.m.f 1.08V?

A potentiometer wire of length 100 cm has a resistance of 10 ohm. It is connected in series with a resistance and a battery of emf 2V and of negligible internal resistance. A source of emf 10mV is balanced against a length of 40 cm of the potentiometer wire. What is the value of the external resistance?

A galvanometer has an internal resistance of 1.0 ohm. It gives maximum deflection for current of 50 mA. Show how it can be converted into (i) a voltmeter with a maximum reading a of 2.5 volts, (ii) an ammeter with a maximum reading of 2.5 A.

A copper wire has a diameter of 0.5 mm and a resistivity of 1.6×10^−6 ohm-m. How much of this wire would be necessary to make a resistance of 10 ohm?