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-voltage itself does nothing
Be a little careful with putting it that way. Voltage causes current to flow, if there is a complete circuit. Without voltage, nothing will happen in a circuit.
But, just because you measure voltage, this doesn’t mean that current is flowing. For example, if you have an open switch in a circuit, you will measure voltage across that switch, but it is “potential”. Since the switch is open, no work is being done in that circuit. But we know if we close the switch, current will flow and work will be done.
As for the quiz question you are talking about, “select the true statement about voltage in a series circuit”, your answer was: “The first load always drops the most current.”
As you can probably see now, there are several problems with that statement. There is no such thing as “dropping current”, since current is constant in a series circuit. Also, if we were talking about dropping voltage, then it is the resistance of a load that determines the amount of voltage drop, not where the load is in the circuit relative to the other loads. One more thing – in an AC circuit, current moves back and forth, so there is no “first” load.
The correct answer, of the choices we gave, is, “The sum of the voltage drops across each load will equal the supply voltage.”
Otherwise, your statements look fine.
One thing I find helpful is to remember that parallel circuits are just series circuits that are tied to the same power supply. So, each “branch” is just a series circuit.
Hi Desert,
This is good stuff to get straight. I’ll go through the concepts:
A load is a component that will do work when current flows through it. Work is something we can detect with our senses, such as heat, light, motion. (So, yes, a light bulb is a load.)
For a load to do work it needs power: voltage AND current.
Voltage alone creates the potential for work to be done. Voltage and a complete circuit will cause electrons to move (current), which will result in work being done by any loads in that circuit.
In a series circuit, the current is the same at every point in the circuit. That current is determined by the voltage supply and the total resistance in the circuit.
A circuit will have a given power supply voltage (120vac, 240vac, 12vdc, etc.). As current flows through a load, it will create a voltage difference (we call it “drop”) across each load. The amount of each individual voltage drop is proportional to the resistance of each particular load. The sum of the voltage drops will equal the source voltage.
In the circuit with several bulbs in a row, remember: the current will be the same through the whole circuit. If those bulbs are identical, then each would have the same amount of voltage drop, and the sum of those voltage drops would equal the source voltage.
Does that help?
Don’t be too hard on yourself! The Midterm is a challenge for most students. It’s designed to really help some of the material we’ve been teaching click in. It takes many students 2 or 3 attempts to pass, but the effort pays off.
Hi Michael,
It’s just the way you are rounding the 1/30 result. It is actually 0.0333333….
So, if you use a calculator in a way that preserves those decimal points, you end up with 18.75. If you round down to just the 0.03 then you end up with 20.
It’s not a very significant different when we’re talking about resistance.
okay – I just did that for you!
The GE example (around 5-6 minute mark) had a 12vdc voltage, so yes – that was the other answer.
Hi Ruslan,
The reason you know you are missing half the voltage is that you have zero voltage drop across the heater. No current is flowing through it, no work is being done.
This means that one of the lines is open, and the 120vac you are measuring from each side of the heater wrt N is coming from the same source – either L1 or L2.
This is like the last question we asked you on the Midterm exam.
So, the correct answer would be #2 above.
Does that make sense?
Now I’m wondering if Neutral is not switched for the ignitors?
You are wondering correctly!
I said:
See if you’re getting 120 vac from P20-2 to P21-1 on the electronic relay board with both bake and broil turned on.You can’t turn bake and broil on at the same time, for one thing.
You’ll probably need to see the answer choices again to figure this one out. Do you want me to go ahead and reset the quiz for you?
No – it’s washing clothes that are too clean. That has a similar effect as using too much detergent, since there isn’t the dirt, etc. on the clothing to react with the detergent.
Hi Joe,
I reset you! Heckuva week for me, too 😀
🙂
Two of those answers are correct, including your first choice of “no heating”. What is your best guess as to the second one?
that’s correct!
As for the switches, I’ll have to bring in some more expertise on this and get back to you.
and also tell me which switch you are asking about
Okay, let’s see if you can figure out the correct answer to #2 on the Unit 4 quiz.
Here are the possible answer choices. Two of them are correct:
Through H2 to L2 in the infinite switch
Through the surface element
Through the light’s bimetal switch
Through L1 to H1 in the infinite switch
It’s hardwired into L1
Through the protector bimetal -
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