(a) Explain, giving reasons, the basic difference in converting galvanometer into (i) a voltmeter and (ii) an ammeter.
(b) Two long straight parallel conductors carrying steady currents `I_(1) and I_(2)` are separated by a distance 'd'. Explain briefly, with the help of a suitable diagram, how the magnetic field due to one conductor acts on the other. Hence deduce the expression for the force acting between the two conductors. Mention the nature of this force.

Explanation

(a) (i) In converting a galvanometer into a voltmeter, a very high suitable resistance is connected is series to its coil. So, the galvanometer gives full scale deflection.
(i) In converting a galvanometer into an ammeter, a very small suitable resistance is connceted in parallel to its coil. The remaining pair of the current i.e. (I-Ig) flows through the resistance. Here I= Circuit current
Ig = Current through galvanometer.