(a) Why does a fully calibrated voltmeter never give the correct value when
measuring the voltage in an electrical circuit (assume that it is used at the same
temperature that it was calibrated at)?
(b) What steps can be taken to reduce the measurement error?
(c) In the circuit shown in Fig. 3.9, the resistor values are given by R1 ¼ 500U;
R2 ¼ 500U; V ¼ 12 V. The voltage across AB (i.e., across R2) is measured by a
voltmeter whose internal resistance is given by: Rm ¼ 7500U.
(i) What will be the reading on the voltmeter?
(ii) What would the voltage across AB be if the voltmeter was not loading the
circuit (i.e., if Rm ¼ infinity)?
(iii) What is the measurement error due to the loading effect of the voltmeter?