Answer to Question #216349 in Electrical Engineering for Fredy

Question

Circuit diagram of ammeter-voltmeter method of unknown resistance measurement. The voltmeter has a resistance of 5000 ohms and the full scale current of the ammeter is 1ampere. The accuracy of ammeter-voltmeter is +or - 0.5% at full scale. In the measurement the reading were 0.55ampere and 37.6ampere. calculate, 1.measured value of the resistors.

2. Calculate true value of the resistor

3.calculate error in ammeter reading

4. Calculate percentage error in ammeter reading at 0.55ampere

Answer 1

Part 1

$R_m=\frac{V}{I}=\frac{37.6}{0.55}=68.36 \Omega$

Part 2

$R= R_m*\frac{1}{1-\frac{R_m}{R_v}}= 68.36*\frac{1}{1-\frac{68.36}{5000}}=69.307 \Omega$

Part 3

0.5 % of I _{full scale}

$\frac{0.5}{100}*1= 0.005\\ Ammeter \space reading \\ (0.55+0.005) or(0.55-0.005) \\ I_1=0.555 A\\ I_2= 545 A$

Part 4

Percentage error in the ammeter

$\frac{\Delta I}{I}*100\\ \frac{0.555-0.545}{0.55}*100\\ 0.018*100\\ 1.81 \%$