Argand diagram, phase difference & power

[eddievic]

Homework Statement

The potential difference across a circuit is given by the complex number

V=40+j35volts

and the current is given by the complex number

I=6+j3 amps

a) sketch the appropriate phasors on an Argand diagram.
b) Find the phase difference between the phasors for voltage V and current I
c)Find the power (watt) given that

power = VxIxcos∅

The Attempt at a Solution

a) Argand diagram attached (I wonder have I maybe took this too literal as it seems too simple?)
b) tan(V)=35/40=0.875=0.17883 rads
tan(I)=3/6=0.5=0.46365 rads
∅=V-I=0.25518 rads
=14.6°
c)P=VIcos∅
V=√40^2+35^2=53.151
I=√6^2+3^2=6.7082
so substituting into equation
(53.151)(6.7082)(0.9676)=345 watts

 

[barryj]

Your plot for V is backwards on your attachmnet

 

[eddievic]

Your plot for V is backwards on your attachmnet

how so?

 

[barryj]

Looks like you have V = 35 + j40 plotted. I looks OK.

 

[eddievic]

Ah right thanks for there'll

 

[eddievic]

Silly phone should say reply :-)