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Hi Wyatt,
Think of it in terms of a failure sequence and also the temperatures at which the compartments normally operate.
A normal freezer is at around zero degrees, but customers usually won’t detect a problem in the freezer until it gets closer to the freezing/melting point (the temps will “seem okay” to the customer). However, a healthy fridge is at 34-40 deg, and food spoilage will start as low as 45-50 degrees. This is where we will get the phone call from the customer.
In the initial stages of a defrost system failure in a single evap unit, the system can usually still create enough cold air to keep the freezer relatively close to its normal range, but without adequate air flow / chilling (as the coils get increasingly frosted over), it won’t be able to transfer enough cold to the FF compartment. Left uncorrected, the freezer will begin to get significantly warmer as the frost continues to build.
Does that make sense? Let me know.
exactly! Only the lightbulb will have voltage drop, since it is the only load in the circuit.
#26: you said that the fuse is a switch, and that switches don’t drop voltage.
Remember – measuring voltage is measuring a *difference* in charge between two points. If a closed switch acts like a wire, there will be no measurable voltage because the charge is the same.
Voltage *drop* is only measured across a functioning load (when current is flowing through, causing the load to do work).
Fuses are not a load.
Does this clear it up? Please tell me more about what you are thinking. This can take some effort to really nail down!
#7 – yes, you are measuring potential voltage from L1, but with an open neutral the current is not able to flow.
#26: the question is
For the light to be on, what is the correct voltage drop across the fuse?
If you measured voltage across a fuse in a normally functioning circuit, what should you measure?
#7: if the open is on the L1 side, how are you measuring 120vac? Remember – N is the reference point.
Well, zero voltage drop across a known-good load, when you know there is some voltage present, means you have an open (no current is flowing).
You measure the full 120vac. So what does that tell you about which side of the circuit has the open?
Oops – we were posting at the same time. I said you were correct about the fuse not dropping voltage – and that’s what we ask in the question.
The load in the circuit (the bulb) will drop the voltage. Make sense?
Correct! So that’s your answer.
We threw a lot of info at you in this question (which is similar to what happens on a service call), but you just need to think about that one fact – a fuse is basically a switch and thus won’t drop any voltage.
Correct! And do switches drop voltage?
Hi Matt,
First ask yourself a question: is a fuse a load? Remember, pretty much any component in a circuit is either a switch or a load. What is a fuse?
Hi Bryan,
The material we put in our courses is what we know, from many years of experience, to be the foundational information and skills that a capable appliance tech needs to have. In order to be able to troubleshoot electrical systems, you not only have to be able to read a schematic and devise a testing strategy, then you have to interpret the measurements you get – which can sometimes be tricky.
To do this well, you have to have a really good feel for basic circuits and electricity. Ohms Law simply describes how the electrical properties that you need to understand relate to each other. So that’s the main way it’s useful to an appliance tech – to first learn about electricity, then to have something to use when needed to interpret the various measurements you’re taking with your meter(s). There’s no other way to have a solid, functional understanding of how electricity works.
So, its initial usefulness is as an important part of the learning process. An experienced tech who has a good understanding of circuits and electricity will no longer have to do a lot of actual calculations using Ohm’s Law equations, but they still can come in handy now and then when you encounter an unusual head-scratcher type of a scenario.
Hope that helps!
Ah – that is something we picked up at a manufacturer’s training. From Miele, if my memory serves. I don’t know how to obtain one. Are you Miele authorized?
I’m glad you love this stuff! And you are getting close.
This is great because we have identified one area of misunderstanding you have about current in a series circuit.
If you need to, go back and review a little bit of our instruction about current – how electrons flow. In a circuit, if one electron is moving, they are all moving. And all at the same rate. Picture a line of billiard balls that are all touching each other, with no extra space anywhere. If you push the one on the end, they will all move at the same rate. If you stop the one on the front end, they all stop. Electrons behave in that kind of way. What that rate (current flow) is will be determined by the total resistance of the circuit, not by the individual load they are going through at a particular moment in time.
Again – this is for loads in series, not parallel.
Look at the equation you gave in 4.A. I = E / (R1+R2). You are saying there that the current is the voltage divided by the total resistance. That math equation is showing what I said above, basically.
So the circuit current is 6.48 amps, at both R1 AND R2.
Let me know if that makes sense to you.
Good to hear back from you!
Good answers so far.
3. Does current vary at different points along a series circuit, or will it always be the same?
4. Based on that answer, how do you calculate current in the circuit?
Hi Mike,
Glad to help!
(Note that I changed the title of your topic to the unit where you scored a 70%.)
This is THE most common unit in this module for students to struggle with, so don’t feel bad.
First of all, look at Question 6. The thing that is wrong about the answer you chose is not the number. We were asking for the reading on an ammeter (also sometimes called an amp-meter). Does that mean we were looking for voltage or current?
Then for 7 and 8, we’ve got two loads in a series. I’m going to step you through this a bit with questions.
1. What is the source voltage for this circuit?
2. What do you know about the behavior of current in a series circuit?Answer those and then we’ll continue on.
Hi David,
It’s been awhile since I’ve watched those videos – I’m assuming this is something mentioned there. Are you talking about the tool for Miele dishwashers?
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