A device ‘X’ is connected to an a .c source. The variation of voltage, current and power in one complete cycle is shown in Fig 7.5.
(a) Which curve shows power consumption over a full cycle?
(b) What is the average power consumption over a cycle?
(c) Identify the device ‘X’.
(a)
Curve A shows the power consumption over a full cycle. As power is given by: Power = Voltage × Current
Increase in amplitude Power Consumption is given as
Here, V is the rms voltage, V0 is the maximum amplitude of the voltage, ω is the angular frequency and t is the time period.
Thus the power curve will have maximum amplitude represented by curve A
(b)
As Power consumption over a cycle includes Positive cycle as well as negative cycle. The average power consumption would be zero.
(c)
From the graph, the current leads the voltage by 90°. In capacitors the current leads the voltage by 90° .
Hence, X is a Capacitor.