2007-02-15 03:01:51 · 5 answers · asked by Anonymous in Science & Mathematics ➔ Physics
A DC ammeter is nothing but a moving coil meter connected seriesly in the circuit, and it will move when a DC current passes through it, according to the direction of current flow. Now imagin you connect this meter in an AC circuit [say 50 hz] the coil will move [thearetically] to and fro 50 times in a second, practically you won't see this because of the damping mechanism on the moving coil won't allow the coil to move with such speed.
2007-02-15 03:30:14 · answer #1 · answered by Holmes 3 · 0⤊ 1⤋
Because they are completely different. A DC ammeter will output some average value of the signal in question. An AC current varies sinusoidally and has a zero average value. Most likely, a DC ammeter will read out 0 on a DC ammeter. An exception to this would be if the averaging in the ammeter is "faster" than the frequency of the current. In this case, you may see values on the ammeter going up and down quickly (or seemingly repeating randomly).
2007-02-15 03:08:01 · answer #2 · answered by deken_99 2 · 0⤊ 0⤋
AC current switches from a peak positive value to a peak negative value at a specific frequency - 50 or 60 Hz, depending on what side of the Atlantic you're on. The "average" power is zero. DC amperage does not switch - it maintains a steady peak value. A DC amp meter measures this steady DC value and averages the AC value - which will necessarily be zero on a DC meter - or, if the meter's quick enough, it will display random values of plus and minus DC current. An AC meter will rectify this current and display the RMS value of the positive or negative going wave.
The RMS value of the AC current is directly related to the same current that would occur at the same DC current.
2007-02-15 03:45:48 · answer #3 · answered by LeAnne 7 · 0⤊ 0⤋
AC voltage switches from positive 240 volts to negative 240 volts at 50Hz (well in the UK it does - I think its 60 in the US)
50Hz means 50 times per second.
A DC Ammeter would not appreciate this in the slightest - in fact if it is a coil meter (not digital) I think it would die....
2007-02-15 03:08:12 · answer #4 · answered by Doctor Q 6 · 0⤊ 0⤋
it would measure its value as average over a cycle and the average value of current and voltage over a cycle is zero so dc ammeter cannot measue ac
2016-05-24 03:27:09 · answer #5 · answered by Anonymous · 0⤊ 0⤋