Susan Brown

[Susan Brown]

Hi Abbey,

It all depends on what information you are given.

If you look on the Ohm’s Law “Pie chart”, there are 3 equations that can be used to calculate current (I). You choose the one that best fits the scenario you have.

What info about the circuit do you have?

[Susan Brown]

Hi Desert,

The first step on this question is to figure out how the loads are laid out in relation to the others. Are they in parallel? Series? Are all loads receiving current? (that’s an important one!)

The “Zen trick” is a great help in figuring this out.

let me know what you think.

[Susan Brown]

LOL – Some threads can confuse rather than clarify, depending on the number of people chiming in – you can always start your own if there’s something you’d like to try to clear up!

[Susan Brown]

Hi Robert,

The Danfoss app can be set to either gauge or absolute.

[Susan Brown]

Hopefully you just misheard something we said.

I’m very glad to hear about the new job and that your being in our training helped! It doesn’t surprise me – we do have a good reputation! It’s too bad his other techs won’t take him up on the offer.

[Susan Brown]

but I had found a statement from the training that current was the same in parallel circuits

Can you tell me where this is in the course?

“current varies in each branch of a parallel circuit depending on the total resistance of loads in each corresponding branch of the parallel circuit. However, the current will be the same outside of the branches.”

Yep, that’s it. Also, the total current will equal the sum of the currents in the individual parallel circuits.

If you look over our quiz questions for Units 4 and 5, it’s pretty clear how current behaves in series and parallel circuits.

[Susan Brown]

Hi Sean,
Have you watched the video at the end of Unit 3 where we show how to do the calculation, using slightly difference numbers for resistance? Try imitating our calculation yourself on paper. If there’s a step you don’t quite follow, tell me what it is and I’m happy to help you further.

[Susan Brown]

You figured it out! And so glad to hear you’re enjoying the course so far – thanks for letting us know!

[Susan Brown]

Yes, that’s what it is good for!

[Susan Brown]

Current depends on the resistance in a circuit.

The only generalization you can make about parallel circuits is that they each have the same source voltage, since each branch is tied to Line and N (or L1 and L2 if a 240 circuit).

The current going through each parallel branch will depend on the resistance of the load(s) in the branch. Only if each branch had an identical load would the current would be the same.

Does that help?

[Susan Brown]

You got it! The key to this question is recognizing the shunt. Everything falls into place after that.

[Susan Brown]

When the detector switch is closed, they will all go through that circuit, since it has no load.

By definition, (which we gave in Unit 1 and also talked about in more detail in Unit 5) all the current will go through a shunt, if one is available. It’s how loads are controlled in a lot of circuit configurations – switches sometimes close to create a shunt that bypasses a load so that it won’t do any work.

An unintended shunt (that happens by accident) is a “short”.

[Susan Brown]

Hi Shawn,

A lot of people call those “finger drivers”. We got ours at our local hardware store, but here’s an example at Amazon:

https://amzn.to/2ZsUz3v

[Susan Brown]

Hi Bill,

I moved your question to a new topic, since it didn’t really have to do with that other thread.

See the video in this forum topic – it should help you!
https://my.mastersamuraitech.com/appliance-repair-course-support/student-forums/topic/calculating-equivalent-resistance/

[Susan Brown]

There’s a big difference between a path with resistance (a load) in it and a path with none. A shunt is not like a parallel circuit, because ALL of the electrons will choose that path over one with a load in it.

Keeping that in mind, take another look at the circuits and see what you think.

[Author]

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