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A moving coil instrument gives full deflection with 15 mA. The instrument has the resistance of 5 ohms. If a resistance of 0.80 ohms is connected in parallel with the instrument, the instrument will be capable of reading upto

Given:

Resistance of instrument Rm = 5 ohms Shunt resistance Rs = 0.80 ohms Full scale deflection current Im = 15 mA = 0.015 A

To find: Instrument current I

We can use the formula relating the shunt resistance, instrument resistance, and full scale deflection current to the instrument current:

Rs = Im * Rm / (I - Im)

Substituting the given values, we get:

0.80 ohms = 0.015 A * 5 ohms / (I - 0.015 A)

Multiplying both sides by (I - 0.015 A), we get:

0.80 ohms * (I - 0.015 A) = 0.015 A * 5 ohms

0.80 I - 0.012 = 0.075

Adding 0.012 to both sides, we get:

0.80 I = 0.087

Dividing both sides by 0.80, we get:

I = 0.109 A or 109 mA (rounded to three significant figures)

Therefore, the instrument current is 109 mA.