Question
Download Solution PDFA galvanometer coil has resistance 20 Ω and the metre shows full scale deflection for a current of 2 mA. How will you convert the metre into an ammeter of range 0 to 6 A?
Answer (Detailed Solution Below)
Detailed Solution
Download Solution PDFCONCEPT:
- A galvanometer can be converted into an ammeter by connecting a shunt resistance in parallel to it.
- The shunt resistance should have very low resistance.
- So, the ammeter (the parallel combination of galvanometer and shunt resistance) will have low resistance.
- To convert a galvanometer into an ammeter of current rating ‘I’, a small resistance ‘S’ (shunt resistance) is connected in parallel across the galvanometer.
\({V_g} = \left( {I - {I_g}} \right)S = {I_g}{R_g}\)
Where Vg is the voltage across the galvanometer, I is the current in the circuit, Ig is the current in the galvanometer, Rg is the resistance of the galvanometer and S is the resistance of the shunt.
CALCULATION:
Given:
Galvanometer coil has resistance Rg = 20 Ω
Full-scale deflection current Ig = 2 mA
Ammeter range I = 6 A
S = IgRg/(I - Ig)
⇒ S = 0.002 × 20/(6 - 0.002)
⇒ S = 6.66 mΩ
Last updated on Jun 19, 2025
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