(d) Least count of voltmeter
(e) Zero error of voltmeter
( Range of voltmeter
Note: To get correct reading, subtract zero error from recorded readings.
Ammeter
R = VAI
(Ohm)
Voltmeter
Resistor
S.
Reading (in ampere)
No.
Reading (in volt)
(92)
Observed
Observed
(Ampere)
(A)
Corrected
(Volt)
(V)
Corrected
(Ampere)
(A)
(Volt
(V)
1.
Ist resistor
(R)
2.
3.
2nd resistor
1
(R)
2.
3.
Series
1
combination of
Rand R
2
Answers
What is the use of least count and zero error in ammeter and voltmeter? How does it affect the readings?
Where can you find data about materials online?
Least count for a measuring instrument means the smallest value that can be measured using the instrument. This can be calculated by dividing the maximum value that can be measured using the instrument by total number of divisions on the scale. Least count gives the resolution of the instrument.
The above Voltmeter can measure up to 10 Volts and has a total number of 25 divisions. Hence it’s least count is 10 V/25 divisions =0.4 V/division, meaning as least as 0.4 Volts can be measured using this voltmeter. Similarly for the shown ammeter least count can be calculated as 50 A/25 divisions=2A/division and hence as least as 2 Amperes can be measured using it.
Based on scale of operation, one can choose the meter with the appropriate Least count.
Ammeter or Voltmeter is said to have zero error if their pointer doesn’t read zero when it is supposed to read i.e. when not connected to the circuit.
Before making connections, this zero error needs to be noted, if any. After connecting the meters to the circuit and upon measurement, this zero error needs to be accordingly added to or subtracted from the shown reading to get the actual reading.
Similar to least count, zero error is also applicable to other measurement devices.
hope it helps you ❤️.....