Susan Brown

[Susan Brown]

Sort of! But you’ve got a mistake. The source voltage is 120vac. All of the loads combined must drop 120 – as you knew in your first response. So, calculating 120 as the drop across just one of the loads can’t be right.

The correct formula for voltage drop is E = I x R. We give you each resistance, so you’ve got to figure out what to plug in for the circuit current. (And what you just did isn’t correct.)

Does current vary throughout the series circuit or is it the same?

(And – for another hint – look at what you did for Question 3 on the Midterm.)

[Susan Brown]

Hi Gilbert,

No, 0.013 is not correct. You would expect to get something less than 103, obviously, but not *that* much less!

However, 1/.013 does get you the correct answer, which is around 78 ohms.

Check out this previous forum topic where we show a similar calculation in more detail, and see if this helps:
https://my.mastersamuraitech.com/appliance-repair-course-support/student-forums/topic/calculating-equivalent-resistance/

Let me know!

[Susan Brown]

“Mega-” is a million of something. So, 1 Mega-watt is 1 million watts (1,000,000 watts). But you can change it to any other unit of measure, too. A “Giga-” is 1 billion (1,000,000,000) of something. That’s why converting a mega-watt to a giga-watt results in a smaller number. 1 mega-watt is 0.001 giga-watt. Is that what you wanted to know?

[Susan Brown]

Hi Terry,

This can seem like a fine point, but we do emphasize (and want to encourage) techs to think in terms of “power” when it comes to loads doing work. The specs for loads are often given in watts (which is voltage times current). For a load to do its work properly, there must be the correct amount of both voltage and current to create the necessary wattage. (So, the correct answer was “power”.)

[Susan Brown]

Hi Kenneth,

What is your question about 4 megawatts? Are you trying to convert it to something different?

[Susan Brown]

Hi Joshua,

No point in googling other resources when you’ve got the ultimate resource right here – Team Samurai! A lot of what your tuition pays for is the ability to ask us questions here in the Forums.

We need to address these questions one at a time. Let’s start here with question 7.

(By the way – I’m going to hide the question in your post above, so that other students won’t see it before they take the Midterm themselves.)

Question 7 has two parallel circuits, and at first we assume everything is behaving normally – current is flowing through both branches.

Then, the top circuit (with the element in it) fails open. You gave us the correct answer for what happens to current in that branch. But then we ask what will happen to the voltage drop and current in the fan motor circuit.

Do you recall what we taught about parallel circuits, in terms of how a failure in one branch affects another?

[Susan Brown]

Hi Joshua,

Happy to help! First of all, these loads have different resistances. Will that affect the voltage drop across them? Isn’t there a relationship between resistance and voltage that we taught?

[Susan Brown]

Hi Mohamed,

We’re talking about the size of the letters or numbers used on a schematic. They tend to use large letters for the various safety warnings (which professional techs are already aware of). But the key information needed for troubleshooting – specifications for the loads, for example – are often in small letters/numbers. In other words, for a professional tech, the most important information is usually the smallest.

[Susan Brown]

Hi Robert,

Think of their function in the circuit, and that will help you know the answer to this. Also, we teach this in Mod. 3, unit 7 (skim through the text of that unit and you’ll see).

[Susan Brown]

Or better yet, look at this:

https://my.mastersamuraitech.com/appliance-repair-course-support/student-forums/topic/please-read-how-to-post-a-topic-in-the-forum/

[Susan Brown]

Hi Kenneth,

This is the Ask the Teacher Forum! If you want help with something, you can start a new topic. Did you watch this video on how to do that?

https://mastersamuraitech.com/site-help-videos/#forums

[Susan Brown]

Do you check the little box that says “Notify me of follow-up replies via email” ? That’s a very helpful thing to do. As for looking at this page, it doesn’t auto-refresh. You have to reload the page to see new replies.

I’ve reset you for that quiz. For future reference, there’s a Quiz & Exam Reset Request form that we want you to use. Just look under the “Contact Us” item in the main menu.

Also, keep in mind that Module 3 is very challenging. Please keep asking questions here in the Forums so we can help you.

We didn’t discuss Question 11. We have a video in Unit 3 that goes over this calculation (with slightly different numbers for the resistances). Watch that again, and try to do the same calculations we show you in your own notebook. If there are steps that you don’t quite follow, just let us know and we can help you.

[Susan Brown]

E or V is fine for volts. Our chart in Unit 3 uses E. Did you see my reply above?

[Susan Brown]

Actually, the chart in Unit 3 uses “E” for voltage, but some other charts do use “V”. As long as you know either of those letters is “voltage”.

So, you are given “P” and “E”, and we ask you to find R.

This means you need to find an “R = …” equation in the pie chart that uses E and P. Can you see which one?

[Susan Brown]

Hi Rees,
Thanks for posting a question here! Yes, it can take a little time getting used to working with equations and such if you haven’t had much experience with it. But we are happy to help.

First of all, the Basic Electricity module is one of the toughest ones for many of our students. I tell you that just so you won’t get discouraged. Some guys mistakenly think if the 3rd module is difficult, they won’t be able to handle the rest of the course. Not so. So, hang in there!

Secondly, some of these units do require going through a few times. Are you pausing the videos as you watch them to take notes? Do you try to recreate the calculations that we show you in your notebook? These are the types of study habits that will help you.

The other thing that would be helpful is to identify more specific points in the unit where you don’t follow what we are showing you, so we can give you more help here in the Forums.

Let’s start with Question 7. “A heating element has a rated wattage of 5600 watts and is connected to a 240 V AC source. What is the resistance of the heating element?”

The first way to organize your thoughts is to identify what information we are giving you, and what we are asking you to find.

Given:
heating element – 5600 watts
power source – 240vac
Find:
resistance of element

Can you tell me what the symbols (letters) are for those 3 items? (the ones we used in the Ohm’s Law chart)

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