Susan Brown

[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.

[Susan Brown]

Hi John,

You’ve got the correct quantity (“about 1350”), but what are “heat units”? That’s not a normal way for us to quantify heat (and thus not the correct answer).

There was another choice for an answer that uses the correct units – do you know what that would be?

[Susan Brown]

The concept of this problem is very similar to the “loose connection” problem that you successfully calculated on the Midterm Exam (Question 6). Two loads in series, and calculating the heat produced by one of the loads in particular. Look back over your answer for that and let me know if you still understand what you did there.

[Susan Brown]

Hi Phillip,

Are you talking about this question?

You’re working on an appliance with the circuit configuration shown below. R1 = 5 ohms. R2 = 32 ohms. If everything is working correctly, what is the expected heat produced by R2?

[Susan Brown]

Hi Phillip,

See if this video helps: https://youtu.be/cLkeBsDXjZc

For any more detailed advice on service calls, please use Appliantology.org.

[Susan Brown]

Great!

[Susan Brown]

In the problem you are talking about from the Midterm, you are given the resistance of each load, and you calculated the circuit current in the previous question. You should then be able to do a calculation for of voltage drop across each load. Each load has the same current going through it.

[Susan Brown]

Hi Mariah,

Don’t you also know the circuit current?

Here are the critical things to remember about a circuit with loads in series:

1. The current will be the same at every point in the circuit.
2. The current flowing through each load will produce a voltage drop across that load.
3. The sum of those voltage drops through all of the loads will equal the source voltage.

Look at the Ohm’s Law equations in Unit 3. If you know the circuit current and you know each load’s resistance, do you see how you could calculate the voltage drop across each load?

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