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### #2 Electricity [Post Homework Here]

Posted: **Thu Nov 01, 2012 12:19 am**

by **ThePyroElectro**

The next course is coming up tomorrow (11/1/2012) here:

http://www.pyroelectro.com/edu/basics/electricity/Post your homework answers here to compare with everyone else!

### Re: Electricity [Post Homework Here]

Posted: **Sun Nov 04, 2012 2:43 am**

by **STLShawn**

If you are like me, and by the time you log in to the BBS and begin to answer, you have forgotten the questions,,,, here's the link, Right click and choose "open in new tab" or "Open in new window".

http://www.pyroelectro.com/files/edu/basics/electricity/homework.pdf and the video was at:

http://www.pyroelectro.com/edu/basics/electricity/HOMEWORK QUESTION 1What is Electricity?The flow of current (Electrical Energy) from one point to another.

HOMEWORK QUESTION 2What ‘Units’ are used to describe electrical Voltage, Current and Power?

(Hint: ‘Units’ of length are commonly in meters, inches, feet or miles)Voltage: Volts (V)

Current: Amperes (A)

Power: Watts (W)

HOMEWORK QUESTION 3If you know that your desktop printer runs off of a 12 Volt power supply and uses 250

miliamp, how much power (in Watts) does your desktop printer require to operate?((Ohhh trick question,, cheeky devils,, making us look up Miliamp,,, 1000 mA (Miliamp) = 1 A, or 1mA=.001 A ))

W=A*V

W=.25 *12

W=3

HOMEWORK QUESTION 4What is the difference between the voltage of a battery and the voltage from a power outlet in

your home?Batteries = DC Current (Direct current that flows in one direction)

Outlet = AC Current (Power that changes it's flow from + to - and back at a certain frequency,,, how frequent? 60 times per second in the US)

### Re: Electricity [Post Homework Here]

Posted: **Sun Nov 04, 2012 10:26 pm**

by **ThePyroElectro**

Well done Shawn!

I hope others don't copy all your answers

...and if they do I hope they learn from them!

### Re: Electricity [Post Homework Here]

Posted: **Mon Nov 05, 2012 1:33 pm**

by **Blackgoo**

1-The flow of electrons

2-Voltage(V), Ampere(Amp), Watts(W)

3- If 250 miliamp=0.25 amps, then w=0.25*12= 3w

4- Battery have a DC current, and the outlet an AC current

And i got a question, what is the need or bennefit from a current than change between + and - constanly? (edit for adding the question)

### Re: Electricity [Post Homework Here]

Posted: **Mon Nov 05, 2012 6:19 pm**

by **ThePyroElectro**

Blackgoo wrote:1-The flow of electrons

2-Voltage(V), Ampere(Amp), Watts(W)

3- If 250 miliamp=0.25 amps, then w=0.25*12= 3w

4- Battery have a DC current, and the outlet an AC current

And i got a question, what is the need or bennefit from a current than change between + and - constanly? (edit for adding the question)

Correct answers Blackgoo (and nice name)!

As for need/benefit for DC vs. AC - These are the two forms of electricity that exist in nature. Lemons/Limes/Oranges all have a DC voltage that is static from their citric acid content. AC electricity is from the more 'wavey' side of nature (like wind/water) and so its natural form is changing back and forth (+ to -).

So there is no specific 'need' for AC, it's just a part of nature! But there are specific benefits for using AC over DC and DC over AC. For example: Batteries can store DC really well, so most small electronics run off of DC. Alternatively, it's really easy to efficiently increase AC voltage with transformers and efficiently transport that energy over power lines.

### Re: Electricity [Post Homework Here]

Posted: **Thu Nov 29, 2012 7:17 pm**

by **mattg**

These tutorials are great! I am looking forward to all of these lessons. Now, to comment:

The formula sheet for this lesson, I think has two typos, regarding converting Amps and Watts:

0.0001 kA = 0.1 A = 100 mA NOT 0.0001 kA = 1 A = 1000 mA

As well,

0.0001 kW = 0.1 W = 100 mW NOT 0.0001 kW = 1 W = 1000 mW

Just wanted to point it out that there are too many zeroes someplace.

Finally, Q4. Difference between the VOLTAGE in a battery and that in your home (others have pointed out the difference is current, but the question was about voltage).

Isn't the difference the voltage range (is that the right word?). DC is a constant voltage value, whereas AC is a variable voltage (ranging between +120V to -120V). Or is the answer that house voltage is typically higher than battery voltage - I have never seen a battery with a 120V value!

### Re: Electricity [Post Homework Here]

Posted: **Thu Nov 29, 2012 8:33 pm**

by **ThePyroElectro**

mattg wrote:These tutorials are great! I am looking forward to all of these lessons. Now, to comment:

....

....

....

Isn't the difference the voltage range (is that the right word?). DC is a constant voltage value, whereas AC is a variable voltage (ranging between +120V to -120V). Or is the answer that house voltage is typically higher than battery voltage - I have never seen a battery with a 120V value!

Hi Matt!

All good answers. And thanks for telling me about the formula sheet's extra 0's, should be fixed now.

There are many ways to answer that question, which is what I encourage -- thinking! When I wrote out the question, I was hoping to hear something along the lines of: the voltage is alternating at 60 Hz between +120/-120 from a house-hold wall socket, while the voltage from a battery is constant and typically stable. But both of your answers are correct!

Commercial batteries rarely exceed +12v or +24v, but you can always connect them 'in series' to bump up the voltage (a topic for another lesson).

### Re: Electricity [Post Homework Here]

Posted: **Sat Dec 01, 2012 8:54 am**

by **karin91**

What is electricity?

Electricity is the flow of electrical charges (free electrons) in a conductor from one point to another, this flow is called current.

What ‘Units’ are used to describe electrical Voltage, Current and Power?

power in Watt, current in Amp, voltage in Volt.

If you know that your desktop printer runs off of a 12 Volt power supply and uses 250

miliamp, how much power (in Watts) does your desktop printer require to operate?

Power: V*I

0.25A*12V= 3W

What is the difference between the voltage of a battery and the voltage from a power outlet in

your home?

Battery have DC a direct current (undirectional) and voltage is always positive.

Power outlet have AC “alternating current”, a current that alternate its direction of flow around a circuit from positive to negative, so voltage vary from positive to negative.

### Re: Electricity [Post Homework Here]

Posted: **Tue Dec 04, 2012 5:50 am**

by **ThePyroElectro**

karin91 wrote:What is electricity?

Electricity is the flow of electrical charges (free electrons) in a conductor from one point to another, this flow is called current.

...

...

Power outlet have AC “alternating current”, a current that alternate its direction of flow around a circuit from positive to negative, so voltage vary from positive to negative.

Hi Karin,

All good answers. Thanks for posting them!

### Re: #2 Electricity [Post Homework Here]

Posted: **Fri Jan 25, 2013 1:09 am**

by **jonnyquin**

HOMEWORK QUESTION 1

What is Electricity?

A flow of electrons (electric current) from one point to another

HOMEWORK QUESTION 2

What ‘Units’ are used to describe electrical Voltage, Current and Power?

(Hint: ‘Units’ of length are commonly in meters, inches, feet or miles)

Voltage is meassured in Volts, current inAmperes and power in Watts

HOMEWORK QUESTION 3

If you know that your desktop printer runs off of a 12 Volt power supply and uses 250 miliamp, how much power (in Watts) does your desktop printer require to operate?

If we consider that P=V*I, then P=12*0.250= 3 Watts

HOMEWORK QUESTION 4

What is the difference between the voltage of a battery and the voltage from a power outlet in your home?

The voltage of a battery is always constant, that is, it is direct current whereas the outlet´s changes or oscillates between +230 and -230

### Re: #2 Electricity [Post Homework Here]

Posted: **Fri Jan 25, 2013 9:39 pm**

by **ThePyroElectro**

jonnyquin wrote:HOMEWORK QUESTION 1

What is Electricity?

A flow of electrons (electric current) from one point to another

HOMEWORK QUESTION 2

What ‘Units’ are used to describe electrical Voltage, Current and Power?

(Hint: ‘Units’ of length are commonly in meters, inches, feet or miles)

Voltage is meassured in Volts, current inAmperes and power in Watts

HOMEWORK QUESTION 3

If you know that your desktop printer runs off of a 12 Volt power supply and uses 250 miliamp, how much power (in Watts) does your desktop printer require to operate?

If we consider that P=V*I, then P=12*0.250= 3 Watts

HOMEWORK QUESTION 4

What is the difference between the voltage of a battery and the voltage from a power outlet in your home?

The voltage of a battery is always constant, that is, it is direct current whereas the outlet´s changes or oscillates between +230 and -230

Hi Jonny!

All your answers are correct! +230v ~> -230v....It sounds like you're from Europe, Australia or Africa!

### Re: #2 Electricity [Post Homework Here]

Posted: **Fri Feb 01, 2013 11:42 pm**

by **jonnyquin**

Aye! hahaha! well, i couldn´t keep the secret any longer...Actually I´m on the western african shore..the Canary Islands. That´s the voltage we use know though 40 or 50 years ago 110V was very common

### Re: #2 Electricity [Post Homework Here]

Posted: **Thu Apr 04, 2013 8:03 pm**

by **HEGHELON**

What is Electricity?

HOMEWORK QUESTION 1

What is Electricity?

The flow of electric or current from one point to another

HOMEWORK QUESTION 2

What ‘Units’ are used to describe electrical Voltage, Current and Power?

Voltage is Volts(V), current in Amperes(A) and power in Watts(W)

HOMEWORK QUESTION 3

If you know that your desktop printer runs off of a 12 Volt power supply and uses 250 milliamp, how much power (in Watts) does your desktop printer require to operate?

power, P=V*I, then P=12*0.250= 3 Watts

HOMEWORK QUESTION 4

What is the difference between the voltage of a battery and the voltage from a power outlet in your home?

The voltage of a battery is always constant(unidirectional), that is, it is direct current whereas the outlet´s changes or oscillates between +V and -V , the actual values depend on a number of factors.Such the country etc.

### Re: #2 Electricity [Post Homework Here]

Posted: **Tue Apr 09, 2013 7:15 pm**

by **ThePyroElectro**

HEGHELON wrote:What is Electricity?

HOMEWORK QUESTION 1

What is Electricity?

The flow of electric or current from one point to another

HOMEWORK QUESTION 2

What ‘Units’ are used to describe electrical Voltage, Current and Power?

Voltage is Volts(V), current in Amperes(A) and power in Watts(W)

HOMEWORK QUESTION 3

If you know that your desktop printer runs off of a 12 Volt power supply and uses 250 milliamp, how much power (in Watts) does your desktop printer require to operate?

power, P=V*I, then P=12*0.250= 3 Watts

HOMEWORK QUESTION 4

What is the difference between the voltage of a battery and the voltage from a power outlet in your home?

The voltage of a battery is always constant(unidirectional), that is, it is direct current whereas the outlet´s changes or oscillates between +V and -V , the actual values depend on a number of factors.Such the country etc.

Hello Heghelon,

All your answers were correct. Good job!

### Re: #2 Electricity [Post Homework Here]

Posted: **Sat Jan 03, 2015 5:11 pm**

by **Kungfugrip**

1. What is Electricity?

The flow of electric current.

2. What ‘Units’ are used to describe electrical Voltage, Current and Power?

Voltage(V), Amperes(A), and Watts(W)

3. If you know that your desktop printer runs off of a 12 Volt power supply and uses 250 milliamp, how much power (in Watts) does your desktop printer require to operate?

250 miliamps=.25 amps

12 x .25 = 3 watts

4. What is the difference between the voltage of a battery and the voltage from a power outlet in your home?

Battery:

Direct current always positive

Outlet:

Alternating current. Variable