# Power loss

Discussion in 'Homework Help' started by kvi037, May 17, 2013.

1. ### kvi037 Thread Starter New Member

May 17, 2013
17
0
Hi,

Can anybody help me with this problem?

The voltage across the inductance and resistance in series LR circuit is
v= 141,4 cos wt and the current through the resistive portion of the circuit is iR = 2,80 cos (wt-pi/6). Calculate the power loss for the circuit.

Correct answer should be 173 watts

I appreciate it a lot if you can help me

Thanks!

2. ### t_n_k AAC Fanatic!

Mar 6, 2009
5,448
783
What working can you show thus far?

3. ### kvi037 Thread Starter New Member

May 17, 2013
17
0

I started to figure out Z by:
Z= Û/Î*agle(-pi/6) = 100/1.97* angle (-pi/6) = 50.75 + j0.46

P = i^2 *R = 1.97 ^2 A *50.75ohms = 198.4 W

But this is not giving me the right answer. Do you have som suggestion for a better way to do it?

4. ### t_n_k AAC Fanatic!

Mar 6, 2009
5,448
783
Your Z value is wrong. Probably because you are using your calculator in degrees mode rather than radians mode. The angle ∏/6 is in radians.

kvi037 likes this.