A moving coil milliammeter having a resistance of 10 ohms gives full-scale deflection when a current of 5 mA is passed through it. If the instrument is to be used to measure current upto 1 A.
Right Answer is:
A resistance of 0.502 Ω must be connected parallel with the resistance of the ammeter
As we know that in ammeter the resistance is connected is connected in parallel.
The resistance of milliammeter Rm = 10 ohms
Full scale deflection current Im = 5mA = 0.005A
To measure current upto 1 A. The Resistance of the shunt Rs
Rs = ImRm ⁄ (I − Im) = (0.005 × 10) ⁄ (1 − 0.005)
Rs = 0.5025 Ω