Susan Brown

[Susan Brown]

That’s correct!

[Susan Brown]

Which of the following is NOT one of the points made about voltage and current in the video for this lesson?

There is no absolute 120 volts out there somewhere
There is no absolute 10 amps out there somewhere
All voltage measurements must be made in comparison with some other point.
We arbitrarily designate the earth as having a charge of zero.
Voltage is a difference in charge between two points in an electric circuit.

[Susan Brown]

Good job!

[Susan Brown]

Here’s a hint: there are 4 correct answers to this question.

[Susan Brown]

No, it shouldn’t make a big difference at all. It is just in the section about electric dryers that we talk about L1-L2. Otherwise, all the information will be good for you.

[Susan Brown]

Hi Adrian,

Yes, this difference in power supply is the only significant difference you will find in the course due to the fact that you are in Europe and we are in North America.

In Europe, you don’t have the split-phase power like we do. Your Line – N is around 230vac, and as I understand it, all of your appliances and electrical devices run off of that.

Nearly all of our home appliances (and other electric items) run off of 120vac (Line – N).

The only appliances that run off of 240vac (L1-L2) in the US are electric dryers and electric ovens.

So even though our split-phase power is not directly relevant to where you live, it will benefit you to learn this, since it will deepen your understanding of electricity works.

[Susan Brown]

What do you want to mean with the expression “as far as the battery is concerned, the configuration are the same”?

I’m not sure where exactly we say this (if it’s in a video, it would be helpful to give me the time in the video where it is said), but it sounds like what we say when we are showing that schematic configurations can be drawn in different ways, but actually showing an identical configuration (which means, the way things are arranged or laid out). In other words, an electron would see them as being the same.

And another thing,the formulas from the ohm law’s are equals?Example from the Power formulas(P=ExI is not the same with P=IxIxR).

Yes, they are. For example, E=I x R. So, if you take P=I x E and then put “I x R” where the E is, you get P= I x I x R

Short and shunt

These are both based on the same fact: if an electron has two paths available to it, and one of them has zero resistance, but the other one has a load, it will take the path with zero resistance 100% of the time.

A short is a fault condition where something happens that causes a path for electrons to flow (a complete circuit) from the power supply to N (or ground) that does NOT have a load (resistance) on it. So, there’s nothing to slow down the flow of electrons. This will usually cause a blown fuse or some other failure.

A shunt is a deliberate circuit design that creates an alternate path for electrons to flow around a load, but there is still at least one other load present in the overall circuit, so you don’t get the fault described above. Usually the shunt is controlled by a switch.

[Susan Brown]

Hi Adrian,

A loose connection would be something like a wire that is pulling away from the connector, or the connector itself not being firmly seated onto the connection point. It could also be a terminal that wasn’t crimped or clamped correctly.

Any time wires are connected to each other or something else, but the connection becomes loose.

You are welcome to ask things like this any time. Besides technical terms that may confuse you, we sometimes use slang as well that you might have a hard time following.

[Susan Brown]

You need to know the definition of EEPs. Here it is from Module 5, Unit 4:

The two characteristics of EEPs are:

1) They have electrical continuity with each other. In other words, if you measure the resistance between two points that are electrically equivalent, you will measure zero ohms. It would be like measuring the resistance in a section of wire.

2) There is zero voltage difference between points that are electrically equivalent. If you were to measure voltage across two EEPs, you would read zero, even if both points were at 120vac.

You can only identify EEPs by studying the schematic and finding testing points at a convenient location (like the control board) that are electrically equivalent to the testing points that you would use if you were at the load of interest itself. It’s often just a wire that comes from the load to the control panel, that has no other loads or open switches along the way.

It may take some practice. Look for videos of ours that demonstrate using EEPs. We’ve got lots of them! Anytime you see us taking measurements at the control panel, you’re probably seeing us using EEPs.

[Susan Brown]

No problem! So, you understand it now? We’re always happy to answer questions here.

[Susan Brown]

Hi there! Yes, voltage measurements are always live (connected to the power supply). That’s where the voltage comes from.

[Susan Brown]

Hi Dean,

We discuss and demonstrate Half Splitting in the second half of this unit:

https://my.mastersamuraitech.com/module-5/using-schematics-to-troubleshoot-appliances/

[Susan Brown]

Okay, I see what’s going on.

1/30 is 0.033333…

So, the difference is just in the rounding. You used 0.03.

1/.0533 = 18.75

Not a significant difference as far as ohms readings go, so either result would be fine.

[Susan Brown]

1/.02 + 1/.03 = 1/.05

That’s not quite the formula, and it’s also not the way you can add fractions. Let’s back up a bit and step through it.

The two resistances are 30 and 50 ohms.

So the formula is 1/(1/30 + 1/50)

The rule with multi-step calculations is that you always do what’s in the parentheses first.

What is 1/30 + 1/50? (It is not 1/80… use your calculator to turn each fraction into a decimal number… 1 divided by 30, etc.)

Then add those two decimal numbers together.

Then you would do 1 divided by that result.

What do you get?

[Susan Brown]

What is Kirchhoff’s Law? (from Unit 8)

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