in a given ammeter, a student sees the needle indicates 12 divisions in ammeter while performing an experiment to verify ohms law. If ammeter has 12 divisions between 0 and 0.5 A, then what is the value corresponding to 12 divisions?
Answers
Zero error:
If the pointer of the ammeter or voltmeter is exactly at zero, when it is not connected to the circuit, then the instrument has zero error. If the pointer is above the zero mark, the the zero error is negative. The number of divisions it is above the zero mark are to be subtracted from the reading.
That is, the Final reading = Reading on the instrument, when connected in circuit - Zero error
If the pointer is below the zero mark, the zero error is positive.
That is, the Final reading = Reading on the instrument, when connected in circuit + Zero error
Least count:
If a voltmeter has 20 divisions between 0 mark and 0.5 V mark, then its
Least count = Minimum measure of unit between two marks / Number of divisions
= 0.5/20
= 0.025 V or 25 mV
In a similar way least count of ammeter is calculated.