Susan Brown

[Susan Brown]

He would have been referring to a closed switch having very little voltage drop.

Current flowing through a component with resistance creates a voltage drop. A closed switch has essentially no resistance. (It’s not absolutely zero, but for the circuits that we deal with in appliances, it’s close enough.) So for our purposes we would say it has no voltage drop.

An open switch has infinite resistance – no current is flowing – so the voltage difference across the switch is NOT voltage drop. It’s just regular potential voltage.

[Susan Brown]

Hi Joe,
you are correct for #4 and 22.

For #20 you’ll have to see the choices again and figure out which one is correct.

[Susan Brown]

Yes – it’s fine. But that needs to be pointed out to the Appliantology administrator, so that he’ll know you are an enrolled student. I’ve forwarded your email to him.

[Susan Brown]

Hi Shaya,

In a 120 vac circuit, you’ve got Line on one side of the load(s), and neutral on the other.

In a 240 vac circuit, you’ve got L1 on one side of the load(s), and L2 on the other.

They basically work the same way, there’s just a larger voltage difference between the two sides. The electrons still zip back and forth along the two sides of the circuit. Remember, in AC circuits, the current does not just go in one direction.

Does that help?

[Susan Brown]

We don’t mean for it to be tricky. Techs need to keep current and voltage distinct in their minds. It should be as obvious as reading “apples and bananas” that current and voltage are describing very different things. So, it’s a lesson in paying attention to important terminology!

[Susan Brown]

Question #2: Measuring DC current is a measurement you will probably never do as a professional appliantologist.

[Susan Brown]

But based on what you said, if R1 is two times R2, and if R2 is 30, then R1 is 60. R1 + R2 has to be = 120. 60+30 = 90.

[Susan Brown]

Hi Snoopy – that’s a bit more complicated than what we show in the Unit 3 “loose connection” video.

Micah – please watch that video and see if you can follow along the calculation, and let me know.

[Susan Brown]

Hi Don,
I see that you sent in your application for the membership. That will get processed on our end and you’ll get notified by email.

[Susan Brown]

Which question is this for? I need to make sure I give you the right advice 🙂

[Susan Brown]

Hi Micah,

In general, voltage is a difference in charge. Sometimes voltage is measured at some point with respect to neutral.

Voltage drop is specifically measuring voltage difference across a load. When current flows through a load (resistance), it creates a difference in voltage. That’s “voltage drop”.

So, the answer you chose for #1 is true about an electrical load. We were looking for something that is NOT true about a load.

For #7 and #8, we’ve got two loads (heating elements) in series. When current flows through them, they will generate heat. And you can calculate that heat using Ohm’s Law equations. Go back to Unit 3 and rewatch the video about the heat generated by the loose connection. It is a very similar scenario to this one.

Let me know how I can help you further!

[Susan Brown]

So the voltage from N to G is 0.

Correct!

There are two types of AC circuits that we deal with in appliances:

L1-N, which are 120 vac circuits
L1-L2, which are 240 vac circuits.

L2 is not neutral – it is another “hot” line.

#4 – sounds like you’ve got the correct answer now
#13 – answer is “a train on a track”

[Susan Brown]

Hi Joe,

Let’s start with your first question:
Question #2: An AC circuit is properly grounded and supplied with One Million Volts. You have your volt meter and measure the voltage from the neutral wire to ground. What do you see on your meter?

Do you remember that we taught that voltage is not an absolute value of something that exists? Rather, it is always a difference between two points. That’s why when you measure voltage, you have to use two probes.

In this example, we’re saying that we have an L1-N circuit, where L1 is One Million Volts. You take your volt meter and put one probe on the neutral wire, and the other to ground. Is there a difference in voltage between Neutral and Ground?

[Susan Brown]

Hi Don,

You have to be a Tech Member at Appliantology to download manuals.

https://appliantology.org/blogs/entry/1027-tech-memberships-at-appliantology/

[Susan Brown]

Air distribution system and temperature sensing device

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