What would you suggest to a student if while performing an experiment he finds that the pointer/needle of the ammeter and voltmeter do not co-incidence with the zero marks on the scales when the circuit is open? No extra ammeter/voltmeter is available in the laboratory.
Class 10 Electricity
CBSE 2019
3 mark Question.
Answer according to the marks of Question.
Answers
Required Answer :
As pointer of both the ammeter and voltmeter do not co incide with the zero marks on the scales when circuit is open, it indicates zero error in both the instruments. This zero error should be subtracted from the reading taken when circuit is closed.
To get correct readings using these instruments, firstly we should find out the least counts of both the instruments.i.e. the minimum value which can be accurately measured.
Zero error=Initial reading ( in open circuit)=pointer reading (in open circuit) X least count.
To get the actual reading, subtract zero error or the initial reading of the open circuit to the reading when you perform the experiment.
Actual reading=Final reading-Initial reading (zero error)
He should use an ammeter whose machanism is correct for measuring reading.