The excepted
(a) When a multi-meter is to be used, the measurement of d.c current or voltage, the following are the steps to be taken:
- the meter knob is switched to the “DC” section.
- A measurement range with value equal to or greater than the maximum value of voltage or current to be measured is selected.
- Multimeter is then connected (in series for current measurement or parallel for voltage measurement) to terminals from which measurements are to be taken.
- Care must be taken to ensure that the meter’s real lead is connected to the positive terminal and the black lead to the negative terminal.
(b) With reference to the equivalent circuit displayed above, it is clear that
ISRS = ImRm
Since IS = 10 – 0.01 = 9.99A; and Im = 0.01A
It follows that 9.99Rs = 0.01Rm
Therefore RS = (0.01/9.99) Rm
The question was on measuring instruments and very few candidates attempted it. In part (a), the candidates’ responses were scantly coherent.
In part(b), a few candidate wisely avoided the question which could be attributed to the value of the galvanometer’s internal resistance which was not stated.
