A micro-ammeter has a resistance of 100 Ohm anf full scale range of 50micro Ampere. It can be used as a voltmeter and an ammeter of a higher range provided a resistance is added to it. Pick the correct range and resistance combination(s) :-
(A) 50 V range & 10 kilo Ohm resistance in series
(B) 10 V range & 200 kilo Ohm resistance in series
(C) 5 mili ampere with 1 ohm resistance in parallel
(D) 10 mili ampere range with 1 Ohm in parallel
the voltage is given as
V = Ig(G + S)
where
Ig = 50uA = 50 x 10-6 A
G = 100 ohms
S = 200 Kilohms = 200000 ohms
so,
V = 50 x 10-6 x (100 + 200000)
or
V = 10V
.
and
current is given as
I = ((G + S) / S).Ig
so,
here S = 1 ohms
this,
I = ((100 + 1) / 1).50 x 10-6
so,
I = 5 x 10-3 A = 5mA
so,
form the above two sets of values we infer that options (b) and (c) are correct, respectively.