# RL Circuit Refresher

Hi, I have just been refreshing my theory and was going over a parallel RL circuit, like this one.

I tried some values as a test but it doesn't give me the correct answer, for total current. eg if I set
V=10V
R=2.5ohm
jXl=5ohm

Then IR=10/2.5 =4A

IL=10/5=2A

IT=√42 +22 =4.47A

However when I try the formula from the second answer I get 10/(2.5-2j) which following the maths gives me 2.44+1.95j=3.12A

Am I going wrong somewhere or is it the formula?

Thanks

#### Attachments

• vFu2isf.png
131.6 KB · Views: 648
• wSOg5fX.png
36.1 KB · Views: 680

jim hardy
Gold Member
Dearly Missed
However when I try the formula from the second answer I get 10/(2.5-2j) which following the maths gives me 2.44+1.95j=3.12A

A 'Site', you said ? If it's on the internet it must be right, eh ? See my signature..............

see if that works any better.

old jim

#### Attachments

11.2 KB · Views: 229
jendrix and Delta2
jim hardy
Gold Member
Dearly Missed
Oops ----- make that it equals Vin X ( 1/R -j1/ωL )

i put my j in wrong place .

Delta2
Delta2
Homework Helper
Gold Member
Oops ----- make that it equals Vin X ( 1/R -j1/ωL )

i put my j in wrong place .

Seems we cant even trust Old Jim when he posts at the internet with a computer, cause we can never trust a computer with anything important

Ok seriously speaking that was a minor mistake, I didn't notice it either, I just noticed the huge mistake in the algebra in the OP.

jim hardy
jim hardy
Gold Member
Dearly Missed
i do that all the time. I'm just clumsy.

Thanks @Delta2

jendrix
i do that all the time. I'm just clumsy.

Thanks @Delta2

Thanks Jim for clearing that up

jim hardy and Delta2