Phasor Problem: Convert i(rt), i(ct) from i(t)

[teng125]

for i = 0.4A cos (wt + 60) , how do we get i(rt) =0.35A cos(wt + 30) and then i(ct) = 0.2A cos(wt+ 120) ??

 

[teng125]

v = 30V (cos 30 + j sin30) is given

 

[teng125]

the circuit consists of capacitor and resistor

 

[Ouabache]

A good way to present a problem like this is to describe the circuit as best as you can. With your third post, it appears you have power supply V and a capacitor and resistor connected in some fashion. How is your resistor and capacitor connected?

You gave in your first post that the current thru your resistor is at a different angle \theta compared with your capacitor. Do you notice anything special about the difference between the two angles?

 

[teng125]

no,there is just a z and the current and voltage is given,not even a circuit.
the current for capacitor and resistor is the answer and i don't understand how they got the answer

 

[Astronuc]

There are several possible configurations between input and output, based on two components (which component, resistor or capacitor, is first) and configurations series vs parallel vs T.

Is this correct - v = 30V (cos 30 + j sin30) ? Is this at time, t=0?

or should it be 30V (cos (wt+30) + j sin (wt+30)) = 30V e ^{j (wt+30)}?

Then look at the voltage v, and see if it is phase with the current in the resistor.

Welcome to the world of complex analysis.

See also - http://en.wikipedia.org/wiki/Phasor_(electronics)

http://en.wikibooks.org/wiki/Electronics:Phasors