To extend the useful range of a voltmeter, an additional resistor. R series. is

Question

To extend the useful range of a voltmeter, an additional resistor. R series. is placed in series with the voltmeter as shown in the figure. If the internal resistance o f the voltmeter is Ri, V. determine the resistance that the added scries resistor has to have to extend the useful range of the voltmeter. Then, calculate the resistance the series resistor has to have to allow a voltmeter with an internal resistance of 2.00 M Ohm(10_6 Ohm) and a maximum range of 2.00 V to measure potential differences up to 200. V. To extend the useful range o f an ammeter, a shunt resistor. R shunt, is placed in parallel with the ammeter as shown in the figure. If the internal resistance of the ammeter is Ri, A. determine the resistance that the shunt resistor has to have to extend the useful range of the ammeter. Then, calculate the resistance the shunt resistor has to have to allow an ammeter with an internal resistance o f 2.00 Ohm and a maximum range of 2.00 A to measure current* up to 200. A

Explanation / Answer

The meter has an internal resistance of 2M ohms. It takes 2.0 V. for FSD. You want it to read 200V. at FSD.
(2M x 200) - 2M) = series resistance of 398M ohms.
Voltage distribution is 2V. across the meter, and 398V. across the series resistor. Thus, 2/200th. is across the meter as a fraction, and 398/200th. is left, across the series resistor.

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