Defintions- Is this correct?

[mbrooke]

Would this be the correct definition of ampere? I always assumed amps was quantity, or amount of electrons for a given period of time, or technically one columb per second.

Ampere
The ampere (symbol: A) is the unit used to measure
current intensity.

Second in this question would A and D be the correct answer? This is for a 3 volt circuit with a flash light bulb, knife switch and DD battery.

Which of these could be used as a resistor in a circuit?

a. a pencil
b. a gas engine
c. a rubber eraser
d. an electric motor

Third;

Electrical insulators

Some materials do not allow electricity to pass through
them. These materials are known as electrical insulators.
Plastic, wood, glass and rubber are good electrical
insulators. That is why they are used to cover materials
that carry electricity.

Would changing the underline to "pass through them easily. " be more correct or is the definition still off?


4th, would B and C work as an answer?

10. Why is electrical wiring usually covered with a layer of plastic?

a-To make it look pretty
b-To help electricity flow along the wire
c-To make it safe

Just wondering if I could make these better. Working on a teaching tool.

 

[GoldDigger]

Would this be the correct definition of ampere? I always assumed amps was quantity, or amount of electrons for a given period of time, or technically one columb per second.
...
...
Second in this question would A and D be the correct answer? This is for a 3 volt circuit with a flash light bulb, knife switch and DD battery.
...
...
Third
Would changing the underline to "pass through them easily. " be more correct or is the definition still off?
...

Just wondering if I could make these better. Working on a teaching tool.

1. Intensity is probably a poor word to use here, since it has a connotation of something per area or volume, something which has a value at a point.
I would just say unit of current, period, and then make sure you have defined current as quantity of electric charge passing a demarcation (usually a surface) in one second. Historical note: for measurement purposes current was first actually defined in terms of the force between two parallel wire sections at a specific distance.

2. I would say that you can use a motor as a resistor, if you ignore the inductance and do not let the motor spin (producing back EMF) or you can use the graphite core of the pencil as a high value resistor. There were some circuit kits at one time that had you draw your resistors on a substrate using a specific pencil. However in the context of a battery and light bulb I doubt that a typical pencil would allow the bulb to visibly light. You should perform that experiment.

3. Definitely, since except at the quantum level there is no such thing as a perfect insulator.

 

[mbrooke]

1. Intensity is probably a poor word to use here, since it has a connotation of something per area or volume, something which has a value at a point.
I would just say unit of current, period, and then make sure you have defined current as quantity of electric charge passing a demarcation (usually a surface) in one second. Historical note: for measurement purposes current was first actually defined in terms of the force between two parallel wire sections at a specific distance.

2. I would say that you can use a motor as a resistor, if you ignore the inductance and do not let the motor spin (producing back EMF) or you can use the graphite core of the pencil as a high value resistor. There were some circuit kits at one time that had you draw your resistors on a substrate using a specific pencil. However in the context of a battery and light bulb I doubt that a typical pencil would allow the bulb to visibly light. You should perform that experiment.

3. Definitely, since except at the quantum level there is no such thing as a perfect insulator.

This is why I love you guys! Spot on- I will include this explanation in the answer key after I tweak the wording.

Technically for #2, even a spinning motor will act as a resistor in that it take energy to spin the mass of the armature across space and time?


One more:

10- Electrical energy can be stored in a ____________________. (also known as DC current)

The correct answer is battery, however capacitor would work better here technically?

My reasoning is that outside of a capacitor or static electricity across 2 mediums it is physically impossible to "store" electricity. A battery does not hold or store a charge, but rather chemicals that facilitate it.

But then again, there is a potential across a charged battery, extra electrons on one plate a deficiency on another, so a battery is then storing electricity? :?

 

[mbrooke]

One thing I am thinking of explicitly explaining is that plastic/rubber is a poor conductor. Often good enough to do the job at 600 volts and under- but not something you want to use to handle high voltage in a lab experiment...

 

[GoldDigger]

This is why I love you guys! Spot on.

Technically for #2, even a spinning motor will act as a resistor in that it take energy to spin the mass of the armature across space and time?


One more:



The correct answer is battery, however capacitor would work better here technically?

My reasoning is that outside of a capacitor or static electricity across 2 mediums it is physically impossible to "store" electricity. A battery does not hold or store a charge, but rather chemicals that facilitate it.

But then again, there is a potential across a charged battery, extra electrons on one plate a deficiency on another, so a battery is then storing electricity? :?

But a motor (if free to spin) will likely not provide a linear resistance.
The fourth question is made totally unusable by the words in parentheses. Except in an inductor current has nothing to do with energy storage.
You are correct that a battery stores chemical energy that can then be transformed into electrical energy. I would have to say capacitor or inductor as the two answers.

 

[mbrooke]

But a motor (if free to spin) will likely not provide a linear resistance.

My knowledge runs out here- can you clarify.

The fourth question is made totally unusable by the words in parentheses. Except in an inductor current has nothing to do with energy storage.

Got it- I was thinking DC would hint to a battery.

You are correct that a battery stores chemical energy that can then be transformed into electrical energy. I would have to say capacitor or inductor as the two answers.

You would be right.

 

[GoldDigger]

My knowledge runs out here- can you clarify.

Let's assume, for the moment, a DC motor. The relationship between applied voltage and current depends in a complex way on the way the stator and rotor are wound (shunt, series, or compound) and whether or not the motor is free to increase in speed or not (loading and control).
If, OTOH, it is an AC induction motor connected to a constant power load, the current will actually decrease as the applied voltage is increased.

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[mbrooke]

Let's assume, for the moment, a DC motor. The relationship between applied voltage and current depends in a complex way on the way the stator and rotor are wound (shunt, series, or compound) and whether or not the motor is free to increase in speed or not (loading and control).
If, OTOH, it is an AC induction motor connected to a constant power load, the current will actually decrease as the applied voltage is increased.

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I agree.

 

[GoldDigger]

I agree.

And that is not the behavior you expect from a resistor, which was the reason I argued it was not, on further examination, a valid resistor. It is a resistance, or more properly an impedance, but it is not a constant impedance which would allow useful calculations about what is going on in the circuit.

For that matter, the light bulb is a very simple indication of applied voltage and current, but the resistance of the bulb varies with temperature.

 

[Besoeker]

Don't make the answers more complicated than they need be for the target audience.

 

[GoldDigger]

Don't make the answers more complicated than they need be for the target audience.

mbrooke is trying to make it simple but correct for an audience with no advance electrical experience or knowledge. I would not go into that sort of detail with the students.
But as he is designing the course, I feel that mbrooke should know the limits of the simple explanations he is giving to his students and avoid making statements that seem plausible but are in fact not technically correct.

 

[Besoeker]

mbrooke is trying to make it simple but correct for an audience with no advance electrical experience or knowledge. I would not go into that sort of detail with the students.
But as he is designing the course, I feel that mbrooke should know the limits of the simple explanations he is giving to his students and avoid making statements that seem plausible but are in fact not technically correct.

Then, at the level it is pitched, I would say the answers offered are fine except I would have left off the word "intensity" for current. Is 5A more intense than 3A ?

 

[mbrooke]

mbrooke is trying to make it simple but correct for an audience with no advance electrical experience or knowledge. I would not go into that sort of detail with the students.
But as he is designing the course, I feel that mbrooke should know the limits of the simple explanations he is giving to his students and avoid making statements that seem plausible but are in fact not technically correct.

Yup. A bit harder than I thought, but doable. I want to make this relatively simple and understandable, but not to the point where the definitions are technically off or debatable. Some of these students may latter move from HVAC and go onto electrical so I would like this to compliment any more advanced course.

 

[mbrooke]

And that is not the behavior you expect from a resistor, which was the reason I argued it was not, on further examination, a valid resistor. It is a resistance, or more properly an impedance, but it is not a constant impedance which would allow useful calculations about what is going on in the circuit.

For that matter, the light bulb is a very simple indication of applied voltage and current, but the resistance of the bulb varies with temperature.

In that regard I would agree, however a motor would still present voltage drop across the circuit like the light bulb. Would this be ok to tell students?

BTW, the none constant current can be picked up by placing a speaker in series.




One last thing here, this is not mine, but I just want to double check that its correct:


https://fyi.uwex.edu/mrec/files/2011/04/W4.-Biesterveld-NEC-grounding-MREC2010.pdf


Its the most simple and straight forward explanation of grounding and bonding I could find while being correct in all regards.

 

[GoldDigger]

Yes, there will be a voltage drop across the motor.
The presentation on grounding and bonding looks correct and well organized. You can skip the livestock part and probably do not need to add in pool bonding.

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[mbrooke]

Yes, there will be a voltage drop across the motor.
The presentation on grounding and bonding looks correct and well organized. You can skip the livestock part and probably do not need to add in pool bonding.

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I am not an expert in pools, but is there any time when an HVAC tech will touch a pool? I'm thinking a hydronic pool heater but not sure. I know of mansions where the boiler is used to heat the pool via heat exchanger.

 

[GoldDigger]

I am not an expert in pools, but is there any time when an HVAC tech will touch a pool? I'm thinking a hydronic pool heater but not sure. I know of mansions where the boiler is used to heat the pool via heat exchanger.

I guess it is possible. Probably worth at least a passing mention.