posted by Don .
The coil of wire in a galvanometer has a resistance of RC = 78.0 Ù. The galvanometer exhibits a full-scale deflection when the current through it is 0.440 mA. A resistor is connected in series with this combination so as to produce a voltmeter. The voltmeter is to have a full-scale deflection when it measures a potential difference of 21.0 V. What is the resistance of this resistor?