Question

A milli voltmeter of 25 milli volt range is to be converted into an ammeter to 25 ampere range. The value(in ohm) of necessary shunt will be

Answer 1

Given : A milli voltmeter of 25 milli volt range is to be converted into an ammeter to 25 ampere range.

To Find :   The value(in ohm) of necessary shunt  

Solution:

Let say Resistance of multimeter = R

Voltage = 25mV

Current = 25/R  mA

=25/1000R  A

= 1/40R  A

Current across Shunt =  25  -   1/40R  

25 mV = 25/1000  V

25/1000   = S (25  -   1/40R)

=> 1/1000 = S(  1 -  1/1000R)

=> R = S (1000R - 1)

=> S = R/(1000R-1)

1 can be neglected in comparison with 1000R

=> S  ≈  R/1000R

=> S = 1/1000 Ω

1 mΩ  or  0.001 Ω  

The value(in ohm) of necessary shunt will be 0.001 Ω  

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