Chapter 10, Problem 91CP

Analog meters use a galvanometer, which essentially consists of a coil of wire with a small resistance and a pointer with a scale attached. When current runs through the coil, the point turns; the amount the pointer turns is proportional to the amount of current running through the coil. Galvanometers can be used to make a voltmeter if a resistor is placed in series with the galvanometer. Consider a galvanometer that has a resistance of $25.00\Omega$ and gives a full scale reading when a $50-\mu A$ current runs through it.

The galvanometer is to be used to make an voltmeter that has a full scale reading of 10.00 V, as shown below. Recall that a voltmeter is connected in parallel with the component of interest, so the meter must have a high resistance or it will change the current running through the component, (a) What is the potential drop across the series resistor in the meter? (b) What is the resistance of the parallel resistor?

               Av = lo.oo v →