General Questions about Electricity

[imoldernu]

No good place to start, so:

1. Do you know how to calculate your base cost for electricity? Ie. can you give a single answer for the question: What was your total cost per Kilowatt Hour last month. Total cost... not the delivery, not the equalizer, not the taxes, not the contract cost or the state taxes or any other part of the confusion that could make up you electricity bill. Answer should be like this:
$.124 /KWH.

2. When you leave your desktop computer on continuously... the cost per day?

3. If you have dimmer switches on your house lights, does it cost less when they are dimmed, or does the rheostat resistance offset the expected savings?
Same with fans and other variable devices.

3. Can you put a dollar amount on the cost of operating:
- a clock radio or alarm clock.
-A TV in standby mode, vs. off.
-your cable or satellite TV Box.
-the garage door opener
-the light/clock of your microwave or electric range.

4. The charger for your mobile device. Does it use electricity when it's plugged in, or just when it's charging?

5. Different question.... matching your electronic device with the correct charger:
If the original charger was 5V 1.0 Amp. Problem with using a 5V .5 amp or a 6V 1.0 amp?
Is damage likely if a 12V device is plugged in to a 9V charger, or vice versa?

6. Wired telephones operate on 98+ volts but nearly zero amps. Info correct?

7. Do all chargers convert AC to DC?

8. in an emergency, can regulr dry cells be used to power call phones by splicing wires?

9. Why can't a car jumpstart a totally dead battery?

10. Surge protector didn't protect my computer/modem/monitor/ external hard drive from nearby lightning strike. Why not?

11. What result from reversing wires in a wall socket?

12. I have an emergency generator. Am told I cannot hook up to power supply junction box. Why not?

13. How much of a short circuit is required to shut off the circuit breaker in my garage. Ie: dropping an electric razor in the bathroom sink? A hair dryer?
and in the same vein, why doesn't my circuit tester shut down the breaker?

13. Are electronics that are battery operated, negatively affected hen running on "low batteries"?

14. Why do the USB chargers in my computer operate at different amperages than some of my chargers.

15. Empirical observation ...I have bought chargers of all kinds for electronic devices... paid $.10 to $.25 each, and now have about 60 different chargers. No correlation that I can see between Volts, Amps and the plug in terminal... plus I don't understand why some chargers with the same output are very small, while others are five times the size.

Am sure I am showing some ignorance here, but am sincere in wanting to know more... No easy answers online that I can find.

Yeah... slow day...

 

[NW-Bound]

1. Do you know how to calculate your base cost for electricity? Ie. can you give a single answer for the question: What was your total cost per Kilowatt Hour last month. Total cost... not the delivery, not the equalizer, not the taxes, not the contract cost or the state taxes or any other part of the confusion that could make up you electricity bill. Answer should be like this:
$.124 /KWH.

I have "Time of Day" plan that charges differently for on-peak and off-peak hours. However, last month's total cost was $208 for 1978 KWh, so the average cost was a bit more than $0.10/KWh.​

2. When you leave your desktop computer on continuously... the cost per day?

I don't leave them on 24/7. Can measure and figure out if I do that, but have not.​

3. If you have dimmer switches on your house lights, does it cost less when they are dimmed, or does the rheostat resistance offset the expected savings?
Same with fans and other variable devices.

The electronic dimmers use a thyristor that's controlled by the knob to vary the on-time during the sine-wave cycle, or the duty cycle that the device is on. So, it does cost less when dimmed.​

3. Can you put a dollar amount on the cost of operating:
- a clock radio or alarm clock.
-A TV in standby mode, vs. off.
-your cable or satellite TV Box.
-the garage door opener
-the light/clock of your microwave or electric range on you

One can figure most of this out, but I have not bothered. One thing for sure is that a garage door opener motor would use so little, because it operates for 10-15 seconds at a time, and it's for a few times a day. The phantom power to keep the wireless receiver alive takes more energy as it is on 24/7.​

4. The charger for your mobile device. Does it use electricity when it's plugged in, or just when it's charging?

There's always a bit of phantom power. I never measure, but expect it to be 1W or less. Does it feel a bit warm when plugged in? If so, it is consuming power.​

5. different question.... matching your electronic device with the correct charger:
If the original charger was 5V 1.0 Amp. Problem with using a 5V .5 amp or a 6V 1.0 amp?
Is damage likely if a 12V device is plugged in to a 9V charger, or vice versa?

Plugging in an underrated charger, meaning one with insufficient amperage, does not burn it out if the charger has built-in overload protection to save itself, which is often the case. Plugging in a 9V charger in lieu of a 12V one most likely will not work at all, as if it is not even plugged in.​

6. Wired telephones operate on 98+ volts but nearly zero amps. Info correct?

No, it's 48VDC open circuit, and at a current of 24mA when off hook. Ringing voltage is higher.​

7. Do all chargers convert AC to DC?

Yes, because all chemical batteries are DC.​

8. in an emergency, can dry cells be used to power call phones?

Yes, if the voltage is compatible.​

9. Why can't a car jumpstart a totally dead battery?

The starter may need up to 200A+. The jumpstart cable has too much resistance to supply that. Even a near-death battery can provide quite a bit of juice.​

10. Surge protector didn't protect my computer/modem/monitor/ external hard drive from nearby lightning strike. Why not?

It would have to be HUGE!​

11. What result from reversing wires in a wall socket?

The hot wire and the neutral get swapped, and some appliances may rely on the neutral for grounding. I am not sure what UL allows here.​

12. I have an emergency generator. Am told I cannot hook up to power supply junction box. Why not?

You must have a transfer switch to disconnect your home+generator from the power line. Else, you will be trying to power up the entire neighborhood, or electrocuting the utility repairman.​

13. How much of a short circuit is required to shut off the circuit breaker in my garage. Ie: dropping an electric razor in the bathroom sink? A hair dryer?
and in the same vein, why doesn't my circuit tester shut down the breaker?

Breaker's rating is usually 15A. Razor or hair dryer dropped in water won't draw that much. Same with circuit tester. DVM draws microamps, unless set in amperage mode, but then they have internal fuses. You hear a little "poof" when that happens. And if you set it in the high-current range like 10A which is not fused, then there will be BIG sparks at the probe tip!​

13. Are electronics that are battery operated, negatively affected hen running on "low batteries"?

Digital circuits go banana if power is low. Think computer crashes. So, nearly all of them like laptops and smartphones have shutdown logic. Without that, lights blink, random characters appear on screen, etc... Funny stuff, but usually no permanent damage. Well, hard drive data gets scrambled up, and that can be considered permanent damage ...​

14. Why do the USB chargers in my computer operate at different amperages than some of my chargers.

Different devices have different requirements.​

15. empirical observation ...I have bought chargers of all kinds for electronic devices... paid $.10 to $.25 each, and now have about 60 different chargers. No correlation that I can see between Volts, Amps and the plug in terminal... plus I don't understand why some chargers with the same output are very small, while others are five times the size.

Some designs are more efficient than others. Modern power circuits can be fairly small and light compared to older designs, yet handle the same power. It's done with higher switching frequencies in the DC/DC converter, but this is getting too technical.​

Am sure I am showing some ignorance here, but am sincere in wanting to know more... No easy answers online that I can find.

Yeah... slow day...

It's slow here too.​

 

[LOL!]

I can only answer the first question:

Last month's electricity (mostly for A/C) for a 3000+ sq ft McMansion in south Texas was 810 kWH at $.124/kWH. This is 20% less than the same period in 2013. Outside temps for 2013 were very hot, but 2014 is much cooler.

 

[REWahoo]

1. Do you know how to calculate your base cost for electricity? Ie. can you give a single answer for the question: What was your total cost per Kilowatt Hour last month. Total cost... not the delivery, not the equalizer, not the taxes, not the contract cost or the state taxes or any other part of the confusion that could make up you electricity bill.

Yes. Total cost last month: $0.093/kWH

 

[target2019]

Our bill lists the cost per kWh for comparison. It is .0987. You can buy an inexpensive device to measure exactly how much power a plug-in device uses. Look for a Watt Miser, or similar name. Also, there are many, many Web site's which have calculators to help you along.

 

[aaronc879]

Yes. Total cost last month: $0.093/kWH

I guess I should move to Texas. Mine was $.1372/kWH. Then again I only used 231kWH last month. It was that high because I used some heat early in the month. June-Aug are closer to 160kWH because I use no heat or a/c those months. Just a box fan on the really hot days.

 

[REWahoo]

You can buy an inexpensive device to measure exactly how much power a plug-in device uses. Look for a Watt Miser, or similar name.

Kill-A-Watt Electricity Monitor-P4400 at The Home Depot

 

[NW-Bound]

Home Depot used to have these devices on the shelf. They do not stock it at my local stores anymore, and it has to be ordered. I guess people do not care anymore. Or perhaps they do not want to know.

 

[ERD50]

NW-Bound answered it all as well or better than I would, and beat me to it. Especially all the current draws - since we are familiar with stuff like this, we have a handle on how much energy most stuff uses, and only worry about the big ones we can control.

A couple little trivial nit-picks and adds:

6. Wired telephones operate on 98+ volts but nearly zero amps. Info correct?

No, it's 48VDC open circuit, and at a current of 24mA when off hook. Ringing voltage is higher.

I'll add this - Ring voltage is ~100V pk-pk square wave, 20 Hertz (or maybe the old CPS is more applicable?). I've always heard it just called ~ 100V, but I assume that is really the 48V switched, so ~ 96V pk-pk. 1 REN (Ringer Equivalency Number is ~ 7000 Ohm impedance at 20 Hertz, so ~ 7 ma ringer current.).


7. Do all chargers convert AC to DC?

Yes, because all chemical batteries are DC.

I'll nit-pick this - Not a cigarette lighter style car adapter! 12 VDC to a lower device voltage (which might be a switcher, but some are just DC-DC regulators).


14. Why do the USB chargers in my computer operate at different amperages than some of my chargers.

Different devices have different requirements.

Not sure of the question, but USB chargers go into different modes. The 'wall charger' mode can often provide higher current than when in the 'hooked up to a computer port mode' (I forget the actual terms off-hand). And then there is a low power port like some hub outputs (100mA) and powered ports (500mA), USB 3.0 specs are different.

-ERD50

 

[lovingAZ]

Let's all give NW-Bound a round of applause ...... that was awesome!!

 

[yakers]

No good place to start, so:

1. Do you know how to calculate your base cost for electricity? Ie. can you give a single answer for the question: What was your total cost per Kilowatt Hour last month. Total cost... not the delivery, not the equalizer, not the taxes, not the contract cost or the state taxes or any other part of the confusion that could make up you electricity bill. Answer should be like this:
$.124 /KWH.

Like NW-B I have a TOU Time of Use meter with different rates for different times of day, especially important as I have an electric car I charge midnight to 8 AM. I have tons of data but don't want to extract it right now.

2. When you leave your desktop computer on continuously... the cost per day?

Desktop in deep sleep draws very little power. I have a Kill-A-Watt meter but have not examined smaller energy users.
3. If you have dimmer switches on your house lights, does it cost less when they are dimmed, or does the rheostat resistance offset the expected savings?
Same with fans and other variable devices.

No dimmers

3. Can you put a dollar amount on the cost of operating:
- a clock radio or alarm clock.
-A TV in standby mode, vs. off.
-your cable or satellite TV Box.
-the garage door opener
-the light/clock of your microwave or electric range.

have a Kill-A-Watt meter but have not examined smaller energy users.

4. The charger for your mobile device. Does it use electricity when it's plugged in, or just when it's charging?

5. Different question.... matching your electronic device with the correct charger:
If the original charger was 5V 1.0 Amp. Problem with using a 5V .5 amp or a 6V 1.0 amp?
Is damage likely if a 12V device is plugged in to a 9V charger, or vice versa?

6. Wired telephones operate on 98+ volts but nearly zero amps. Info correct?

7. Do all chargers convert AC to DC?

8. in an emergency, can regulr dry cells be used to power call phones by splicing wires?

9. Why can't a car jumpstart a totally dead battery? Totally dead battery is equal to a break in the circuit

10. Surge protector didn't protect my computer/modem/monitor/ external hard drive from nearby lightning strike. Why not?

I have a whole house surge protector, it will protect against pretty much anything but cost $200 plus install

11. What result from reversing wires in a wall socket?

Fuse blown or fire

12. I have an emergency generator. Am told I cannot hook up to power supply junction box. Why not?

You can if you know how but the generator probably does not have enough AMPs for house use. My brother's emergency generator is wired in and delivers 100 AMPS to his house which normally receives 200 AMPS but it is enough power to keep things going.

13. How much of a short circuit is required to shut off the circuit breaker in my garage. Ie: dropping an electric razor in the bathroom sink? A hair dryer?
and in the same vein, why doesn't my circuit tester shut down the breaker?

13. Are electronics that are battery operated, negatively affected hen running on "low batteries"?

14. Why do the USB chargers in my computer operate at different amperages than some of my chargers.

15. Empirical observation ...I have bought chargers of all kinds for electronic devices... paid $.10 to $.25 each, and now have about 60 different chargers. No correlation that I can see between Volts, Amps and the plug in terminal... plus I don't understand why some chargers with the same output are very small, while others are five times the size.

Am sure I am showing some ignorance here, but am sincere in wanting to know more... No easy answers online that I can find.

Yeah... slow day...

Slow day, only a few answers here

 

[rodi]

Our utility company, San Diego Gouge and Extorsion, has tiered rates.
The first 307 kWh are super cheap -$0.02119/kWh (called tier 1 or baseline)
The next 92 kWh are also very cheap - $0.04501/kWh (tier 2)
Then it jumps up significantly for the next tier - $0.22437/kWh.
There's a tier above that but we have never reached it. In fact the bill I received today shows we only had 3kWh in tier 3.

But you said just for price per kWh. There is a bunch of other stuff including the expensive "summer electricity generation" fee - also based on use - that's a flat rate of 0.12916/kWh - or in our case - $51.92
And there's fee differentials, DWR bond charges, etc. Love the bond charges - we paid bond charges to build San Onofre, now we're paying charges to run it despite it being shut down, and they want to charge us to decommission it.

As far as all the other stuff. cable/satellite settops are definitely one of the bigger power sucks. But newer DVRs do have energy star settings. (Basically it turns off stuff like the hard drive, some of the tuners, etc when it's in standby AND not recording.) But cable operators don't always deploy the newer settops - so most folks have old energy hog settops. (I worked in the industry through last week, when I retired.)

clock radios - The newer LED based ones use less power.
usb chargers suck less power than the old pregnant plug types.
My laptop sleep settings are to not just turn off the screen - but to save data to the HDD and almost shut down - it takes a minute or so to wake up - but perhaps I'm saving some power.

My grandmother used to unplug the toaster and "shake off" the excess electricity. She thought if she didn't shake it - it might still have some power in it.

 

[NW-Bound]

6. Wired telephones operate on 98+ volts but nearly zero amps. Info correct?

No, it's 48VDC open circuit, and at a current of 24mA when off hook. Ringing voltage is higher.

I'll add this - Ring voltage is ~100V pk-pk square wave, 20 Hertz (or maybe the old CPS is more applicable?). I've always heard it just called ~ 100V, but I assume that is really the 48V switched, so ~ 96V pk-pk. 1 REN (Ringer Equivalency Number is ~ 7000 Ohm impedance at 20 Hertz, so ~ 7 ma ringer current.).

The following site has more info on the ringing voltage and waveform: Telephone ringing circuits.

As a kid, I opened up a telephone and traced its internal wiring. Found that there was a capacitor in series with the electromagnet coil of the ringer. The cap was to block DC current, but I assumed that it would also resonate with the inductance of the coil for more power to toggle that hammer.

I have not thought about this in years. I do not know if I care to hook up my scope to the phone line to see if they send down sinewave or squarewave to ring it, though I am sure either would work. If there's money in it, I would do it. Getting lazy here...

7. Do all chargers convert AC to DC?

Yes, because all chemical batteries are DC.

I'll nit-pick this - Not a cigarette lighter style car adapter! 12 VDC to a lower device voltage (which might be a switcher, but some are just DC-DC regulators).

You are absolutely correct. I was thinking only of wall chargers.

14. Why do the USB chargers in my computer operate at different amperages than some of my chargers.

Different devices have different requirements.

Not sure of the question, but USB chargers go into different modes. The 'wall charger' mode can often provide higher current than when in the 'hooked up to a computer port mode' (I forget the actual terms off-hand). And then there is a low power port like some hub outputs (100mA) and powered ports (500mA), USB 3.0 specs are different.

-ERD50

The original USB specs call for 500mA max to be drawn from each port at the host, aka computer. There are wall chargers with 1A output, but I do not know what the current spec is.

 

[imoldernu]

It's slow here too.​

Thank you NWB for the time and effort... Appreciate that very much. Not sure I'd be that accommodating.

On the Lightning surge... I wonder if my problem might have come... not from the electric supply, but from the Comcast connection... and the Cat5 cables.
Though the computer, which was off at the time, wasn't affected, the Comcast modem, the Vonage Modem, the Sony media player (cat 5 connection) and the hard drive that was connected to the Sony.... My mistake in the post was that the monitor not affected. The Comcast connection is only to the Comcast modem... not to a box or a TV.

My suspicions about the dimmer control are unfounded. Now, I understand Thyristors, and won't beat up on DW for leaving the Overheads dimmed at night.

Again.. appreciate the time and effort... hopefully not too old to learn new tricks.

 

[H2ODude]

I may be wrong, but as a rule of thumb I assume that if it gets hot (and that's not it's purpose like a heater) it's using significant power. Like the cable box (ever feel it to see how warm they are?) or the home entertainment amp. One of the big hogs in a lot of folks homes is the second fridge sitting out in the garage.

Different subject but on TV's....moved MIL into assisted living and they could not hang the 32" plasma on her wall; too heavy and no studs. So I went and bought a new one. I could not believe how light it was! Could have just about taped it to the wall!

 

[NW-Bound]

You are welcome.

Here's a typical dimmer circuit using a thyristor or Triac. What it does is to pass current through the load only during a portion of the sinewave cycle. The pot (potentiometer) or "volume control" knob lets you vary the length of that portion, hence vary the brightness of the lamp.

In the waveform diagram, what you vary is the position of the vertical edges where the Triac switches on. This abrupt turn-on is also what often generates electrical transients (noise) that bother AM radio, TV, etc...

Though the power consumption is reduced, I think a dimmed bulb may not put out that much light, but still consumes and generates quite a bit of heat. It's because its filament is way below the optimal glowing temperature. In other words, you may get only 25% light, but still use 50% electricity. I would use a Kill-a-watt to measure. But the point is that the dimmer itself wastes little power (it does feel a bit warm though!).

 

[Fermion]

Here is a little tidbit. Did you know that electrons in a wire only move about 3 inches an hour? Talk about slow!

 

[NW-Bound]

It depends on the size of the wire and how much current is being squeezed through the wire, but yes, it is a lot slower than we would think.

From a Web site:

... in a copper wire of cross-section 0.5 mm2, carrying a current of 5 A, the drift velocity of the electrons is on the order of a millimetre per second...

That's 3.6 m/hr or 14 in/hr.

An electron has a charge of 1.602 × 10-19 coulombs, and 5A is 5 coulombs/sec. So, that's 3.12 x 10^19 electrons flowing by every second. Still, there are so many of them in the small wire that they do not have to move very fast to get that flow volume, even at a fairly high current of 5A.

 

[NW-Bound]

So, then how does one explain this "speed of light" that electricity is supposed to propagate at?

 

[Alan]

So, then how does one explain this "speed of light" that electricity is supposed to propagate at?

It is actually the electromagnetic field that propagates at the speed of light, and you get an emf where ever you get an electric current. If the current is alternating then some of that emf can propagate through the air.

 

[REWahoo]

It is actually the electromagnetic field that propagates at the speed of light, and you get an emf where ever you get an electric current. If the current is alternating then some of that emf can propagate through the air.

Should you be using language like that on the forum?

 

[NW-Bound]

It is actually the electromagnetic field that propagates at the speed of light...

True.

But how do you explain in simple terms to a layman that despite the low speed of electrons in a wire, when he turns on a switch, his bulb lights up right away? In the example I cited above, the electron's speed is only 14 in/hr, yet his lamp is many feet away from the switch!

 

[Alan]

Thank you NWB for the time and effort... Appreciate that very much. Not sure I'd be that accommodating.

On the Lightning surge... I wonder if my problem might have come... not from the electric supply, but from the Comcast connection... and the Cat5 cables.
Though the computer, which was off at the time, wasn't affected, the Comcast modem, the Vonage Modem, the Sony media player (cat 5 connection) and the hard drive that was connected to the Sony.... My mistake in the post was that the monitor not affected. The Comcast connection is only to the Comcast modem... not to a box or a TV.

My suspicions about the dimmer control are unfounded. Now, I understand Thyristors, and won't beat up on DW for leaving the Overheads dimmed at night.

Again.. appreciate the time and effort... hopefully not too old to learn new tricks.

The surge protectors that you can buy are for power surges caused by fluctuations in the voltages coming from your power supply, which causes lights to dim and brighten etc.

A lightning strike will send a voltage spike through the wires at thousands of volts and if there is not a physical gap then it is going to travel through the circuits. Fiber optics are great for protecting sensitive instrumentation in structures such as chemical plants where you want to minimize the amount of instrumentation damaged during lightning strikes

 

[Alan]

True.

But how do you explain in simple terms to a layman that despite the low speed of electrons in a wire, when he turns on a switch, his bulb lights up right away? In the example I cited above, the electron's speed was only 14 in/hr, yet his lamp is many feet away from the switch!

But, why does the electron move at all since the current is reversing direction 60 times a second?

 

[Lsbcal]

...(snip)...
15. Empirical observation ...I have bought chargers of all kinds for electronic devices... paid $.10 to $.25 each, and now have about 60 different chargers. No correlation that I can see between Volts, Amps and the plug in terminal... plus I don't understand why some chargers with the same output are very small, while others are five times the size.
...

Some of those cheap chargers could be fire hazards. I would be very careful if they did not come with the original equipment.