# Thread: Defintions- Is this correct?

1. ## Defintions- Is this correct?

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.
Last edited by mbrooke; 03-11-18 at 08:28 PM.

2. Moderator
Join Date
Dec 2012
Location
Placerville, CA, USA
Posts
20,175
Mentioned
3 Post(s)
Tagged
Originally Posted by 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.
...
...
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.

3. Originally Posted by GoldDigger
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?

4. 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...

5. Moderator
Join Date
Dec 2012
Location
Placerville, CA, USA
Posts
20,175
Mentioned
3 Post(s)
Tagged
Originally Posted by mbrooke
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.

6. Originally Posted by GoldDigger
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.

7. Moderator
Join Date
Dec 2012
Location
Placerville, CA, USA
Posts
20,175
Mentioned
3 Post(s)
Tagged
Originally Posted by mbrooke
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.

Sent from my XT1585 using Tapatalk

8. Originally Posted by GoldDigger
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.

Sent from my XT1585 using Tapatalk
I agree.

9. Moderator
Join Date
Dec 2012
Location
Placerville, CA, USA
Posts
20,175
Mentioned
3 Post(s)
Tagged
Originally Posted by mbrooke
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.

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

#### Posting Permissions

• You may not post new threads
• You may not post replies
• You may not post attachments
• You may not edit your posts
•