Why an ammeter can only read DC current and not AC current?
Why an ammeter can only read DC current and not AC current?
An AC ammeter is used for measuring AC current.
A typical moving coil DC ammeter is based on the torque generated on a current carrying loop in a magnetic field provided by a permanent magnet.The torque generated is given as NIABwhere B = strength of magnetic field (T)A = area of coil (m2)N = number of turnsI = current (amp)Since the current in an AC current averages to zero because it is changing too fast even at 60 Hz, the meter does not have time to respond to this because of the inertia of the coil. The average torque a coil experiences in a given time interval is zero and hence there is no deflection. However, hot wire ammeters can be used to measure both AC and DC current. In this case, the deflection is a result of the heat produced which in turn is proportional to the square of the current. Since this is always positive for AC and DC, either can be used.
An AC ammeter is used for measuring AC current.
A typical moving coil DC ammeter is based on the torque generated on a current carrying loop in a magnetic field provided by a permanent magnet.The torque generated is given as NIABwhere B = strength of magnetic field (T)A = area of coil (m2)N = number of turnsI = current (amp)Since the current in an AC current averages to zero because it is changing too fast even at 60 Hz, the meter does not have time to respond to this because of the inertia of the coil. The average torque a coil experiences in a given time interval is zero and hence there is no deflection. However, hot wire ammeters can be used to measure both AC and DC current. In this case, the deflection is a result of the heat produced which in turn is proportional to the square of the current. Since this is always positive for AC and DC, either can be used.
