CBSE Class 10 Science 2018 · Paper 31(B) · Question 27
The range of a milliammeter is 0-500 mA. There are 20 divisions between 0 and 100 mA mark on its scale. During an experiment a student observes ammeter’s pointer at 3rd graduation mark after zero mark when the key is off and the pointer at 15th graduation mark after 300 mA mark when the key is inserted into the plug. Find
- (i)the least count,
- (ii)the zero error with proper sign and
- (iii)the value of current drawn from the battery.
Answer
The least count is 5 mA, the zero error is +15 mA and the current drawn is 360 mA.
(i) Least count mA.
(ii) With the key off, the pointer rests divisions to the right of zero, so the zero error mA (a positive zero error).
(iii) Observed reading mA; current drawn from the battery observed reading zero error mA.
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