Inductive Circuit

[Opara]

Hi, i've been asked to calculate the open-circuit voltage when VL is open.I was thinking that due to infinite resistance the OC voltage would be the voltage across j35.

In which case the voltage divider question would be used.

Would that mean

100*(j35/j35 + j0.3)

Would that mean having to multiply top and bottom by the conjugate of j35+j0.3?

Thanks

[spikeyhead]

Opara said:

In which case the voltage divider question would be used.

Would that mean

100*(j35/j35 + j0.3)

Would that mean having to multiply top and bottom by the conjugate of j35+j0.3?

you can jsut add j35 to j0.3 to get j35.3

then cancel the j terms as they are on both top and bottom, so no need for conjugates.

If you want to analyze the situation with a load, use a Smith chart, but I'll leave that as an exercise for the reader.

[Opara]

Thanks, just working on the voltage VL now.I've never heard of a Smith chart, would that
be the quickest way or could I use loop analysis?

Thanks

[spikeyhead]

Opara said:

Thanks, just working on the voltage VL now.I've never heard of a Smith chart, would that
be the quickest way or could I use loop analysis?

Thanks

If you know how to use a smith chart then it would take no more than 30 seconds to find the answer. Unfortunately it takes a couple of years to learn how to use one.

[Opara]

Ok lol maybe in the future.

My plan was to find overall impedance in order to find the current through the first 0.3 inductor.However my calculations seem to keep coming out wrong.

ie solve (j35(5+j0.3)
_________
5+j0.3+j35

then add this to the 0.3 inductor on the left to give total impedence.Would that work?

Thanks

[spikeyhead]

That should work, just be very careful with the complex arithmetic.

[Simpo Two]

spikeyhead said:

If you know how to use a smith chart then it would take no more than 30 seconds to find the answer. Unfortunately it takes a couple of years to learn how to use one.

Bloody hell, three dimensional logarithms?

'It's full of stars...'

[blinkythefish]

spikeyhead said:

Opara said:

Thanks, just working on the voltage VL now.I've never heard of a Smith chart, would that
be the quickest way or could I use loop analysis?

Thanks

If you know how to use a smith chart then it would take no more than 30 seconds to find the answer. Unfortunately it takes a couple of years to learn how to use one.

You've just given me a flashback from my Electromagnetics course....I fear I shall be having nightmares tonight!