Solved: (a) A voltmeter and an ammeter can be connected as
Chapter 19, Problem 85GP(choose chapter or problem)
(a) A voltmeter and an ammeter can be connected as shown in Fig. a to measure a resistance
. If
is the voltmeter reading, and
is the ammeter reading, the value of
will not quite be
(as in Ohm's law) because some current goes through the voltmeter. Show that the actual value of
is
\(\frac{1}{R}=\frac{I}{V}-\frac{1}{R_{r}}\)
where is the voltmeter resistance. Note that \(R \approx V / I\) if \(R_{V} \gg R\) (b) A voltmeter and an ammeter can also be connected as shown in Fig.
to measure a resistance
Show in this case that
\(R \approx \frac{V}{I}-R_{A}\)
where and
are the voltmeter and ammeter readings and \(R_{A}\) is the resistance of the ammeter. Note that \(R \approx V / I\) if \(R_{A} \ll R\).
Equation transcription:
Text transcription:
frac{1}{R}=frac{I}{V}-frac{1}{R{r}}
R approx V / I
R{V} \gg R
R approx frac{V}{I}-R{A}
R{A}
R{A} ll R
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