SSE JE Electrical Engineering 29 Oct 2020 Shift 2 Papers

Question : 137 of 200

Marks: +1, -0

An MC instrument with internal equivalent resistance of 10 Ω, takes 40 mA to produce full-scale deflection. How do you convert that instrument to measure the current from 0 A to 2 A?

By connecting 0.2041 Ω resistance in series with the instrument
By connecting 0.4082 Ω resistance in parallel with the instrument
By connecting 0.4082 Ω resistance in series with the instrument
By connecting 0.2041 Ω resistance in parallel with the instrument

Validate

Solution:

Meter resistance

( \R _{ \m })=10 \Ω

Full scale deflection current

( \I _{ \m })=40 \mA

Required full scale reading

(\I) =2 \A

∴ The required shunt resistance that should be connected in parallel/shunt will be:

\R _{ \sh }={ \R _{ \m }}/{[{ \I }/{ \Im }-1]}

\R _{ \sh }={10}/{({2}/{40 ×10^{-3}}-1)}=0.2041 \Ω

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