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In moving iron type ammeter the coils has
A large number of turns of thick wire
Large number of turne of thin wire
Few turns of thin wire
Few turns of thick wire
Few turns of thick wire
Quick Summary: Moving iron (MI) ammeters are designed to carry the full load current through their coils. To minimize the internal voltage drop across the instrument and prevent overheating at high currents, the coil is constructed using a few turns of thick wire.
Moving iron (MI) ammeters are designed to carry the full load current through their coils. To minimize the internal voltage drop across the instrument and prevent overheating at high currents, the coil is constructed using a few turns of thick wire.
PlossтАЛ=I2R тАФ Power dissipation in the coil
TdтАЛтИЭI2 тАФ Deflecting torque proportional to square of current
The principle of operation is based on the force of attraction or repulsion between a fixed coil and a movable iron vane placed in its magnetic field. Since current passes directly through the coil, a low-resistance design is required to avoid energy loss (I2R loss) and to ensure the ammeter does not significantly alter the circuit conditions it is measuring.
MI instruments use a stationary coil and a moving soft iron vane.
A thick wire is used to support high current capacity without heating.
Few turns are sufficient because the deflecting torque depends on the current magnitude (I2), not the number of turns alone.
Ideally, an ammeter should have near-zero internal resistance.
Cheap and robust construction
Can measure both AC and DC quantities
Less prone to damage by overloads
Non-linear scale (cramped at the beginning)
Hysteresis error in the iron part
Affected by external magnetic fields
AC power frequency measurements
Industrial control panels for current monitoring
The low resistance ensures that the insertion of the ammeter does not reduce the load current.
Option A and B are incorrect because thin wires would burn out due to high current and high resistance.
Option C is incorrect because thin wire would result in excessive voltage drop across the instrument.
D is correct тАФ Moving iron ammeters utilize a low-resistance coil with few turns of thick wire to handle high current flow with minimal voltage drop.
Always remember: Ammeters are connected in series and should have very low resistance; Voltmeters are connected in parallel and should have very high resistance.