Thermal ammeters are instruments whose operations depend upon the heating effect of current. A moving coil ammeter, a thermal ammeter and a rectifier are connected in series with a resistor across a 230 V sinusoidal AC supply. The Circuit has a resistance of 100 Ω to current in one direction and, due to the rectifier, an infinite resistance to current in reverse direction.
(1) Calculate the readings on the ammeters.?
(2) Calculate the form and peak factors of the current wave.?
any idea on how to solve this or how to draw the circuit ??
2007-04-03 20:02:31 · 1 answers · asked by Prinze , 1 in Science & Mathematics ➔ Physics
Thermal ammeters and voltmeters are used to measure a true root-mean-value of current or voltage. They are measuring based on definition of Power=Energy/Time since (energy is directly related to heat dah)
The 'typical' ammeters and voltmeters measure average or DC values.
The reason why they agree sometimes on displaying the same value is due to calibration of the 'typical' meters to specific frequency and waveform. The thermal meter will serve as a calibrating standard.
Knowledge of a 230 V sinusoidal AC supply definitely helps.
For a sine wave
V (avg) =.637 V(peak)
V (rms)=.707 V(peak)
The 230 Volts AC I would assume to be the rms value.
The peak then V(peak)=230/.707=325 V
Since we have a rectifier only 50% or a half will be detected by either of the meters.
Reading of the avg ammeter (calibrated for DC)
I(avg)=(1/2) x 0.637 x Vpeak/R
I(avg)=(1/2) x 0.637 x 325/100
I(avg)= 1.04A
Reading of the rms ammeter
I(rms)=(1/2) x 0.707 x Vpeak/R
I(rms)=(1/2) x 0.707 x 325/100
I(rms)= 1.15 A
2007-04-04 03:21:03 · answer #1 · answered by Edward 7 · 1⤊ 0⤋