Susan Brown

[Susan Brown]

It’s a good idea to take the time to get these circuit configurations straight in your mind.

The videos at the end of Unit 4 are good to review for this.

Also, do you understand the “Zen trick” we teach in the second video in Unit 5?

[Susan Brown]

When you figure out the answer to Question 3, I think you’ll see what this answer is.

[Susan Brown]

These light bulbs are in series.

In a circuit, you must have a complete path to and from the power supply for current to flow. (If we’re talking about a 120vac circuit, then we need an unbroken path from L1 to N.)

Since the bulbs are in series, there is no alternate path for current to flow. The electrons have to be able to go through both of them in order to have current flow.

What happens to the circuit when a light bulb blows?

[Susan Brown]

Voltage drop is directly proportional to the resistance of a load. In other words, higher resistance equals higher voltage drop.

If you had two or more loads in series, the only way their voltage drop would be identical is if they had the exact same resistance.

[Susan Brown]

Hi Ladarius,

Thanks for posting your questions in the Forums!

It is not a small difference for that switch to be closed – it affects the circuit quite a bit.

What the branch does to the circuit when the switch is closed is discussed in the 3rd video in Unit 5. It is a particular circuit design to control loads (either give them power or divert it).

Do you know what I’m referring to?

[Susan Brown]

Note that the questions don’t tell you the voltage drop – they are asking you to determine the voltage drop. They tell you the lines of voltage that are applied to either side of the load.

Remember voltage drop is created by current flowing through a load.

And current will only flow in a circuit where there is a difference in voltage applied to either end.

[Susan Brown]

Ah! You are looking at the wrong light on the schematic. The “surf ind light” just goes on when any surface element is turned on. The hot surface indicator lights are different. There are 4 of them, and they are switched by a thermostat and come on if the glass temp is >150 deg.

I’m not sure how you got the other questions correct on these quizzes. You should be looking at the LF “hot ind light” (there are 4 of those lights)

[Susan Brown]

Let’s make sure we are looking at the correct light on the schematic. How is the light that you are looking at labeled?

[Susan Brown]

Right, and to get a little more specific, the statement said that the customer set the oven to low bake. A valid problem statement could be “oven won’t heat on bake”, but we gave slightly more specific choices in the question for this Case Study.

[Susan Brown]

Based on what the customer set the range to do, and the results the next morning, what is the range not doing that it should be doing?

[Susan Brown]

The question is asking for the equivalent resistance of two loads that are shown in the diagram.

1. What relationship are those loads in? (series or parallel?)

2. Based on the answer to that question, what is the rule of thumb for the equivalent resistance of loads in that configuration? (We give that in the 3rd video in that unit)

[Susan Brown]

That is the explanation we give as a help for those having a hard time with that question. I’m not sure what your particular question is. These are the same steps that you took to get the answer for Question 6 on the Midterm Exam. We also show a similar calculation in the last video in unit 3 of Basic Electricity.

Is there a specific question you have about this?

[Susan Brown]

Another important characteristic of a load is that when current flows through it, a voltage drop is created.

[Susan Brown]

I assume you are talking about this question:

If the Defrost Heater and the Freezer Drain Heater are operating within specifications, what equivalent resistance would you measure from Pin 13 to Pin 7 in the diagram below:

Here’s your answer:
58 Ω because the equivalent resistance in a parallel circuit will always be equal to the smallest branch resistance.

The heaters are in parallel, with resistances of 58ohms and 320ohms.

Is that the correct rule of thumb for equivalent resistance of parallel loads?

[Susan Brown]

Correct! I’m glad to see that you are making sure that you understand all of the questions and answers.

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