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I know the feeling! I also studied ChemE in college. This electrical stuff takes some work!
Check out this topic and see if it helps:
Hi Jim,
The videos at the end of unit 4 are good to review for this one.
When you have circuits in parallel, and one of the circuits goes open, it will not affect any other of the parallel branches. It will affect the overall current and the equivalent resistance of the entire set of circuits.
The resistance of the bulb is what it is, and the voltage supply to the bulb doesn’t change, so the current through the branch that hasn’t failed will not change.
Does that help?
Happens to us all! 🙂
Hi John,
Electric dryers run on 240vac.(We’ll get to your other two questions shortly!)
Voltage drop is just the difference in voltage measured across a load that is caused by current flowing through the load, and is the same regardless if it’s AC or DC.
E = I x R whether it is AC or DC.
And all of the voltage of the power supply will be dropped across the load(s) in the circuit, regardless of AC or DC.
The amount of heat produced by a given resistance will vary between AC and DC (that’s what the “RMS value” is about). Is that what you are thinking of?
correct!
Hi Nathan,
First of all, 240 and 120 are voltages, not currents.
I’m not sure which question you are asking about. Your topic title says Q.3 ?
The voltages are indicated by whether the circuit is L1 – N or L1 – L2.
Revisit Unit 6 for a review of household power supply.
Hi James,
In this question, R1 is 5 ohms and R2 is 5000 ohms.
We know that voltage drop is proportional to resistance (E = I x R)
We also know that work/power is proportional to voltage drop (P = I x E)
So, you can figure out logically that if R1 is 1000 times less than R2, it will also do 1000 times less work than R2.
The reason your calculation didn’t come up with the same conclusion is that when you are using P=E^2/R in a scenario with multiple loads in series, the “E” has to be the voltage drop across that particular load, not the source voltage.
You could try calculations again to confirm this, but first you would need to calculate the circuit current, I, then you could use P = I^2 x R. You could also calculate the voltage drops across each load and then P=I x E.
Does that make sense?
That’s correct!
The element has continuity.
If current were flowing through it, we would measure a voltage drop from L1-L2. Since we don’t, we know that there’s no current, and we have an open on one side of the circuit. The element is basically going to act as a wire (conductor).
Sketch that out on a piece of paper and think about how the voltage will be present and what you will measure, and see if that helps.
Hi Darryl – did you get my email? I was trying to step you through it there.
Hi Melissa,
No worries! You’ve got a Student Membership over at Appliantology, which is where you can get help on jobs that you are currently doing. Post a topic in the Appliance Repair Tech Forum about this.
Also, you will learn about this technology in more detail in the Oven & Range course.
It takes some effort to learn this stuff – we are glad to help anytime!
That’s a good and important question!
The answer is because of Kirchhoff’s Law. The sum of the voltage drops will equal the voltage supply for a circuit. It is a 120vac circuit, so we know the two voltage drops will need to add up to 120.
60+30 is only 90
80 + 40 = 120vac AND 80 is two times 40.
Make sense?
Hello!
The best place to start is with the Help Page that we linked you to when we emailed you after the midterm.
I’ll resend that email to you – look for it!
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