Susan Brown

[Susan Brown]

Hi Andrea,

#5: The LOI *is* the “thing that ain’t doing its thing.” The LOI is NOT the component that you necessarily think is broken. If a motor isn’t running, it could be faulty, or perhaps it just isn’t receiving power due to a failed switch or board. But either way, it is the obvious item that is not functioning, and where you will start the Ten Step Tango.

#9:
They must be in continuity with each other
There must not be any voltage difference between them

[Susan Brown]

Ok, I think that makes sense.

It’s good that you are thinking this through and asking questions – keep it up! It takes time to really understand this stuff.

Am I right that the earth does not factor in with 240v? Because l1 and l2 complete the circuit?

Correct. Both L1 and L2 are “hot”, but out of phase with each other. Whenever L1 is +120v, L2 is -120v, and vice versa, so there is always a difference between them to drive current.

With Line-Neutral circuits, Line alternates between + and – 120v, while Neutral is always at 0v, which creates that voltage difference.

[Susan Brown]

Hi Clark,

You’re talking about this question, correct?

An AC circuit is properly grounded and supplied with One Million Volts. You are standing barefoot on ground and grab a hold of the bare neutral wire. What happens to you?

The correct answer is nothing.

Remember that voltage drives current. In an active 120v circuit, both sides will have current flowing, but only one side is “hot”. The hot (or “line”) side of a circuit is the side that has voltage. The neutral side is always at ground potential. There is at least one load in the circuit that divides line and neutral.

If you grab the neutral wire while standing on the earth barefoot, current will not flow through you because there is no potential difference between the neutral wire and the earth to push current through the resistance of your body.

If you were not grounded, or the neutral wire was not properly grounded, so that there was some voltage difference between the neutral wire and the surface you were standing on, then some amount of current would flow through you.

As for your last question, the neutral wire coming into the breaker box is tied to earth/ground. But that isn’t the same thing as completing the circuits within our home.

Pop quiz: Think about a 240v (L1-L2) circuit. Does the earth factor in there?

• This reply was modified 10 months, 2 weeks ago by Susan Brown.

[Susan Brown]

Timer contacts are a type of switch. Do you know what voltage you would expect to measure across a closed switch? (which acts just like a wire – no resistance)

[Susan Brown]

Hi Mike,
Your answer was, “58 Ω because the equivalent resistance in a parallel circuit will always be equal to the smallest branch resistance.”
That is close, but not quite right.

You also got the answer incorrect to this question:
Question #12 – In parallel circuits, the equivalent resistance will always be _____ the smallest branch resistance.

Look at the second video in Unit 5, around the 6 minute mark. Do you see what the “rule of thumb” is for equivalent resistance?

[Susan Brown]

Hi Clark,

#2 – You have a circuit with two lightbulbs in series. If one of the bulbs burns out, what change, if any, would you expect to see on an ammeter (current/amps) reading? [emphasis added]

A bulb burning out means that the filament (which is what the electrons go through) has opened. This means that current will stop flowing in the entire circuit, since it is a series circuit. (So the other bulb will have no current and therefore won’t light up.)

Make sense?

[Susan Brown]

Hi Lukas,

For Question 2, watch the video starting at about 1 min. 25 seconds.

For Question 4, he talks about this starting at about the 18 minute mark. The question is referring to where on the *diagram* is the refrigeration effect “happening”.

If you need more help, let me know.

[Susan Brown]

Hi David,
Whether you are doing the calculations yourself using the formulas or using an app, you need to understand the basics of these electrical properties and circuits in order to use them properly.

Things like:

• In a series circuit, the current is the same throughout the circuit, and is determined by the source voltage and total resistance in the circuit.
• When you have loads in series, they will have a voltage drop across them that is proportional to the resistance. In fact, the voltage drop is equal to the current times the resistance. The voltage drops will add up to equal the source voltage.
• Heat generated by a load (P) is also proportional to resistance and voltage drop across the load.

So, with the situation with the loose connection, what we are dealing with is two resistances in series. This results in a higher total resistance, thus a lower circuit current, than when the loose connection was not there.

In order to find the heat generated by just the loose connection, if you use a formula for P that involves voltage, it must the be voltage dropped across the loose connection. If you use the source voltage (e.g., 240v), then you will end up finding the heat generated by the entire circuit.

Does that help?

(I am not sure what you mean by a cheat sheet.)

[Susan Brown]

Hi Allan – please check your email – you are all set!

[Susan Brown]

I reset you

[Susan Brown]

Sure! That will be a good review for you. These units are very common ones to need a little more help on (and often resets). Be sure to ask questions if you need to.

One other thing about your original question. On my dashboard, I can only see the score from the most recent attempt. If you ever have a situation where your first score was higher (and qualified for Certification), you would have to send me the email you received with that score. Otherwise, I’d have no way to know.

[Susan Brown]

Hi Ethan,
First of all – you indicated in your student info that you want to earn Certification for the course. Do you recall the requirements for that?

You must earn 80% or higher on EACH unit quiz, and
90% or higher on EACH exam in the course.

So, not only would you need to retake the exam anyway, but there are two unit quizzes that are below 80%. In order to retake those, you would need to get set back to Mod 4, unit 5.

Let me know!

[Susan Brown]

Hi Michael – I reset it so you can start fresh and answer all the questions.

[Susan Brown]

You got it!!!

(FYI, I’ll hide this answer so we don’t just give it away to other students. They need to experience their own “a-ha!” moment 🙂

[Susan Brown]

Hi Victor – I reset that quiz for you.

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