andy a said:
Using my computer keyboard in the swimming pool tends to severely corrode the contacts I have found.
- Thread starter Texas Bill
- Start date
High Electricity Bills!!!
Using my computer keyboard in the swimming pool tends to severely corrode the contacts I have found.
Sorry! OK, then that's not an American style Cuise Missle. That would be a British Rapier missle she's being propelled about in.
I know it?s quite late in the thread, and the thread diverted away from the original, the electricity cost, but I still would like to put my $0.02 and reply to the post that NotLurkin made of the first page of this thread.
To calculate voltage, V, you multiply currant, I, with resistance, R. (1) V = I * R
To calculate wattage, W, you multiply (2) V x I.
R is constant, it's the TV or any other appliance you may use and it doesn?t change.
To find I we?ll change (1) a bit to be (3) I = V / R
To find W we?ll substitute I with (3) to be (4) W = V * V /R.
From this it is easy to see that if V is smaller so will be the W. What we pay for is the W, wattage, not the V, voltage.
The appliance cannot take more then it gets, stepup transformer or not.
For a lesson on transformer please come to class tomorrow at 08:00 at the beach.
To calculate voltage, V, you multiply currant, I, with resistance, R. (1) V = I * R
To calculate wattage, W, you multiply (2) V x I.
R is constant, it's the TV or any other appliance you may use and it doesn?t change.
To find I we?ll change (1) a bit to be (3) I = V / R
To find W we?ll substitute I with (3) to be (4) W = V * V /R.
From this it is easy to see that if V is smaller so will be the W. What we pay for is the W, wattage, not the V, voltage.
The appliance cannot take more then it gets, stepup transformer or not.
For a lesson on transformer please come to class tomorrow at 08:00 at the beach.
Ohm's Law Simple!!
Ohm's law is not brain surgery, it's very simple!
E= voltage (measured in volts)
I= current (measured in amps)
R= resistance (measured in ohm's)
Ohn's law formula is E=(IR)
E
-----
IxR
to find a value cover the I, E, or R and do the math!
Thank you Boy's and Girl's for your attention, there will be a quiz next week!
John
Ohm's law is not brain surgery, it's very simple!
E= voltage (measured in volts)
I= current (measured in amps)
R= resistance (measured in ohm's)
Ohn's law formula is E=(IR)
E
-----
IxR
to find a value cover the I, E, or R and do the math!
Thank you Boy's and Girl's for your attention, there will be a quiz next week!
John
My, my, aren?t we all the electrical engineers. Class is about to open so please pay attention and enjoy it because this will be the only free lesson I will give.
In DC circuits Ohm?s Law as has been described is true however for Alternating Current (AC) circuits other things need to be taken into account. Ohm?s Law hold true for AC circuits as well but the concepts of resistance, as it applies to AC, is different.
A rotating conductor cutting across a magnetic field produces AC. The rate at which the rotating conductor cut the magnetic field is the frequency and one complete cycle equals 360 degrees. Since the instantaneous induced voltage changes with time, alternating Current (AC) is a sine wave with its maximum value at 90 degrees, its average value at 63.6% of maximum and its Root Mean Square (RMS) at 70.7% of maximum. AC unlike Direct Current (DC) is always changing in value with time and will change polarity on every cycle period (every half cycle).
The reverse is also true. If AC is applied to a conductor, a magnetic field is formed around the conductor. Assume and Alternating Current for the following discussion. (Whatever happens in one cycle happens during subsequent cycles) When the current applied to a conductor is zero, there is no magnetic field around the conductor. As current begins to increase the magnetic field builds up in density, reaching maximum value coinciding with the maximum current point in the positive half cycle. As the current begins to decrease in value, but is still in the same direction, the intensity of the magnetic field also decreases. For all intent and purposes, the magnetic lines of force of the previous high value current in the vicinity of the conductor fall back into the conductor ? the magnetic field collapses, reaching zero intensity when the current reaches zero. As the current begins to flow in the opposite direction (polarity reversal on the next half cycle) the same magnetic effect will take place, except that the magnetic field is of opposite polarity. In the positive half cycle, the magnetic field polarity (rotation) is counter- clockwise and in the negative half cycle the magnetic field is clockwise.
(Action of self induced EMF -Lenz?s Law)
Again assume an Alternating Current but this time through a coiled conductor- consider the coil an AC circuit in which the current is increasing, this will induce an EMF (Electric Motive Force or simply voltage) in the coil. The self induced EMF produced would have a polarity opposite to the applied voltage and tends to retard the buildup of the circuit current (resistance, better known in AC circuits as impedance).
When a changing magnetic field produced by an energized coil cuts the turns of a second coil and induces an EMF in the winding, the action is known as mutual inductance (like in a transformer). The winding from which the magnetic line of force (flux) originates in the primary. The changing current that flows in the primary winding and produces the changing flux is the primary current or inducing current. The winding in which the EMF is induced is known as the secondary. The EMF induced in the secondary is known as the secondary voltage. If the secondary is part of a closed circuit and current flows in the secondary it is secondary current. Mutual inductance is the basis for electrical energy transfer magnetically from one circuit to another in AC circuits and it is the means by which transformers operate.
Impedance (Z - or AC resistance)
Two sources of opposition to current flow exist in the inductor (a coiled conductor - like in a motor or transformer). One is inductive reactance (XL), arising from the action in the inductor, and the other is resistance (R) - resistance which exist in the conductor material, such as, copper and referred to as copper loss. The combined action of XL and R constitute total opposition to current flow known as impedance. Impedance is expressed in terms of Ohms and is indicated by the letter Z. Z = square root of (XL squared + R squared)
(Note impedance can also be composed of Capacitive Reactance (XC) or a combination of XL, XC and R but I will not be addressing XC in this discussion)
With this bit of AC theory under our belts, all heads should be out of obscure orifices, we will proceed to validate the original question as posed by Texas Bill - Does your bill increase if the main service voltage is reduced? The answer is an unequivocal YES!
The most power hungry AC circuits we have in our home contain motors - usually of the induction type. The resistance present in this type of circuits is not fixed and is determined by the instantaneous impedance. When a motor starts it will draw about 3 times its rated current capacity to magnetize its core and service its applied load. After it stabilizes, it will draw whatever current is required to keep it stabilized therefore the current drawn varies because of the load applied to the motor. Hence lighter loads will cause less opposition to motor rotation and less current is drawn. With heavier load it will have the opposite effect. The heavier the load, the stronger the opposition to armature rotation, the more current will be drawn. Now consider a motor that requires 10 amps at 120vac to apply 1100 foot-pound of pressure to a load, 12 amps will be needed at 100vac to carry out the same task. You get nothing for free ? its all physics The current flowing through the motor?s stator (an inductor) will buildup a magnetic field and magnetize the motor?s core. The magnetic field will induce an EMF in the motor?s armature (Mutual inductance), a transformer like action will occur in the motor as more current is need to move its load, the stator will reduce its opposition (it?s self-inductance) and draw more current and delivered it to the armature by way of magnetic flux.
That?s it, class is closed. For the nay-sayers perhaps you could do a bit of research before blowing your horn in such a manner ? it would have saved me all this typing. It is one thing to disagree or question information presented in a post but it is a totally different issue to ?try? to reducible the poster - hmmmm was anyone trying for that?
BTW TigerPilot thanks for offering a tutoring session but I think you should take you own advice.
In DC circuits Ohm?s Law as has been described is true however for Alternating Current (AC) circuits other things need to be taken into account. Ohm?s Law hold true for AC circuits as well but the concepts of resistance, as it applies to AC, is different.
A rotating conductor cutting across a magnetic field produces AC. The rate at which the rotating conductor cut the magnetic field is the frequency and one complete cycle equals 360 degrees. Since the instantaneous induced voltage changes with time, alternating Current (AC) is a sine wave with its maximum value at 90 degrees, its average value at 63.6% of maximum and its Root Mean Square (RMS) at 70.7% of maximum. AC unlike Direct Current (DC) is always changing in value with time and will change polarity on every cycle period (every half cycle).
The reverse is also true. If AC is applied to a conductor, a magnetic field is formed around the conductor. Assume and Alternating Current for the following discussion. (Whatever happens in one cycle happens during subsequent cycles) When the current applied to a conductor is zero, there is no magnetic field around the conductor. As current begins to increase the magnetic field builds up in density, reaching maximum value coinciding with the maximum current point in the positive half cycle. As the current begins to decrease in value, but is still in the same direction, the intensity of the magnetic field also decreases. For all intent and purposes, the magnetic lines of force of the previous high value current in the vicinity of the conductor fall back into the conductor ? the magnetic field collapses, reaching zero intensity when the current reaches zero. As the current begins to flow in the opposite direction (polarity reversal on the next half cycle) the same magnetic effect will take place, except that the magnetic field is of opposite polarity. In the positive half cycle, the magnetic field polarity (rotation) is counter- clockwise and in the negative half cycle the magnetic field is clockwise.
(Action of self induced EMF -Lenz?s Law)
Again assume an Alternating Current but this time through a coiled conductor- consider the coil an AC circuit in which the current is increasing, this will induce an EMF (Electric Motive Force or simply voltage) in the coil. The self induced EMF produced would have a polarity opposite to the applied voltage and tends to retard the buildup of the circuit current (resistance, better known in AC circuits as impedance).
When a changing magnetic field produced by an energized coil cuts the turns of a second coil and induces an EMF in the winding, the action is known as mutual inductance (like in a transformer). The winding from which the magnetic line of force (flux) originates in the primary. The changing current that flows in the primary winding and produces the changing flux is the primary current or inducing current. The winding in which the EMF is induced is known as the secondary. The EMF induced in the secondary is known as the secondary voltage. If the secondary is part of a closed circuit and current flows in the secondary it is secondary current. Mutual inductance is the basis for electrical energy transfer magnetically from one circuit to another in AC circuits and it is the means by which transformers operate.
Impedance (Z - or AC resistance)
Two sources of opposition to current flow exist in the inductor (a coiled conductor - like in a motor or transformer). One is inductive reactance (XL), arising from the action in the inductor, and the other is resistance (R) - resistance which exist in the conductor material, such as, copper and referred to as copper loss. The combined action of XL and R constitute total opposition to current flow known as impedance. Impedance is expressed in terms of Ohms and is indicated by the letter Z. Z = square root of (XL squared + R squared)
(Note impedance can also be composed of Capacitive Reactance (XC) or a combination of XL, XC and R but I will not be addressing XC in this discussion)
With this bit of AC theory under our belts, all heads should be out of obscure orifices, we will proceed to validate the original question as posed by Texas Bill - Does your bill increase if the main service voltage is reduced? The answer is an unequivocal YES!
The most power hungry AC circuits we have in our home contain motors - usually of the induction type. The resistance present in this type of circuits is not fixed and is determined by the instantaneous impedance. When a motor starts it will draw about 3 times its rated current capacity to magnetize its core and service its applied load. After it stabilizes, it will draw whatever current is required to keep it stabilized therefore the current drawn varies because of the load applied to the motor. Hence lighter loads will cause less opposition to motor rotation and less current is drawn. With heavier load it will have the opposite effect. The heavier the load, the stronger the opposition to armature rotation, the more current will be drawn. Now consider a motor that requires 10 amps at 120vac to apply 1100 foot-pound of pressure to a load, 12 amps will be needed at 100vac to carry out the same task. You get nothing for free ? its all physics
The current flowing through the motor?s stator (an inductor) will buildup a magnetic field and magnetize the motor?s core. The magnetic field will induce an EMF in the motor?s armature (Mutual inductance), a transformer like action will occur in the motor as more current is need to move its load, the stator will reduce its opposition (it?s self-inductance) and draw more current and delivered it to the armature by way of magnetic flux. That?s it, class is closed. For the nay-sayers perhaps you could do a bit of research before blowing your horn in such a manner ? it would have saved me all this typing. It is one thing to disagree or question information presented in a post but it is a totally different issue to ?try? to reducible the poster - hmmmm was anyone trying for that?
BTW TigerPilot thanks for offering a tutoring session but I think you should take you own advice.
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Not bad NotLurking.....but please allow me a little room for discussion.
1. The average value of a sine wave is zero. You meant the average value of a full-wave rectified sine wave.
2. Look up Maxwells equations. The magnetic field around a conductor depends on both DC current and AC voltage.
Unfortunately, the transmission line theory and electromagnetic discussion has not answered the original question. In order to answer the question, lots of detail is needed. Here is what we need to know:
3) schematics of the electric power meter. The reason for this is that most single-phase induction type meters actually measure instantaneous power. They do not just measure current. The speed of the disk not only depends on the current being used, it also depends on the line voltage. Therefore, theoretically for these meters....the speed should NOT change....and the answer is NO.....you are not being overcharged. Keep in mind that this depends on the implementation of the meter.
4) How does the power consumption of the appliances change with changing line voltage?
5) Is 80V below the minimum operating voltage of the load?
6) Is the meter properly caibrated? This can be a HUGE source of error. There are several fudge factors that the Electric company uses to come up with your bill?
7) Is there proper power factor correction?
1. The average value of a sine wave is zero. You meant the average value of a full-wave rectified sine wave.
2. Look up Maxwells equations. The magnetic field around a conductor depends on both DC current and AC voltage.
Unfortunately, the transmission line theory and electromagnetic discussion has not answered the original question. In order to answer the question, lots of detail is needed. Here is what we need to know:
3) schematics of the electric power meter. The reason for this is that most single-phase induction type meters actually measure instantaneous power. They do not just measure current. The speed of the disk not only depends on the current being used, it also depends on the line voltage. Therefore, theoretically for these meters....the speed should NOT change....and the answer is NO.....you are not being overcharged. Keep in mind that this depends on the implementation of the meter.
4) How does the power consumption of the appliances change with changing line voltage?
5) Is 80V below the minimum operating voltage of the load?
6) Is the meter properly caibrated? This can be a HUGE source of error. There are several fudge factors that the Electric company uses to come up with your bill?
7) Is there proper power factor correction?
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modongo....
Mondongo, you bring up some good points.
In reference to item #1, I did not state that the average of a sine wave is zero. However I did state that the average is 63.6% of maximum value.
Item #2 - I?m familiar with Maxwell (and his law), Weber, Gauss, Tesla.and also Michael Faraday. In an AC power circuit there in no DC current. In fact, if a DC component is present in a transformer the B-H curve of the core will be altered and the transformer will lose its symmetry. If DC is present in the primary when flux reversal occurs the DC will oppose the magnetic flux reversal and will cause an excessive amount of heat in the core. The dielectric of the magnetic wire will eventually fail and a short circuit will occur ? Destroying the transformer. Also note that induction only occurs in AC circuits not in DC. A DC current flowing through a coil will create a magnet and alter all magnetic properties of an inductor if present ? either transformer or motor.
Actually, magnetism has everything to do with this discussion. What is wattmeter? Is not an induction motor?
You are correct in saying that the question hasn?t yet been proven correct by my previous answer. I was more interested in quashing the erroneous application of Ohm?s law in AC circuits than anything else.
Item #3 ? this is the most compelling point brought forward and to be honest I did not even consider the meter design when I rendered my answer. It really depends on the meter design and line voltage could very well be taken into account.
Item #4 ? is this a trick question? The answer should be obvious from my answer above. Work needs to be done and the cost of doing this work in electricl AC circuits is voltage and current. In circuits that are purely resistive such as light bulbs, irons and water heaters the rate of consumption will actually decrease. Since they don?t contain impedance (reactance) their resistance is fixed thus have a PF of unity and Ohm?s law applies exactly as it does to DC. OTOH, if we are considering AC circuits that have inductance or capacitance reactance then current consumption will increase as voltage decreases.
Item #5 ? if 80vac isn?t within its operating range and it is a reactive load it will go into high current consumption - possibly causing the appliance damage.
Item #6 ? some very good question and food for the thought. I bet that a mis-calibrated meter rips us off more then anything else.
Item #7 - not likely. PF correction has only recently enter the consumer electronics market.
If the meter measures REAL power then I have erred and my answer is WRONG with respect to an increase in your bill. However the meters used here are designed for 120vac and calibrated for that voltage. It would be interesting to find out how the meter?s calibration (accuracy) is affected by a decrease in line voltage.
Mondongo, you bring up some good points.
In reference to item #1, I did not state that the average of a sine wave is zero. However I did state that the average is 63.6% of maximum value.
Item #2 - I?m familiar with Maxwell (and his law), Weber, Gauss, Tesla.and also Michael Faraday. In an AC power circuit there in no DC current. In fact, if a DC component is present in a transformer the B-H curve of the core will be altered and the transformer will lose its symmetry. If DC is present in the primary when flux reversal occurs the DC will oppose the magnetic flux reversal and will cause an excessive amount of heat in the core. The dielectric of the magnetic wire will eventually fail and a short circuit will occur ? Destroying the transformer. Also note that induction only occurs in AC circuits not in DC. A DC current flowing through a coil will create a magnet and alter all magnetic properties of an inductor if present ? either transformer or motor.
Actually, magnetism has everything to do with this discussion. What is wattmeter? Is not an induction motor?
You are correct in saying that the question hasn?t yet been proven correct by my previous answer. I was more interested in quashing the erroneous application of Ohm?s law in AC circuits than anything else.
Item #3 ? this is the most compelling point brought forward and to be honest I did not even consider the meter design when I rendered my answer. It really depends on the meter design and line voltage could very well be taken into account.
Item #4 ? is this a trick question? The answer should be obvious from my answer above. Work needs to be done and the cost of doing this work in electricl AC circuits is voltage and current. In circuits that are purely resistive such as light bulbs, irons and water heaters the rate of consumption will actually decrease. Since they don?t contain impedance (reactance) their resistance is fixed thus have a PF of unity and Ohm?s law applies exactly as it does to DC. OTOH, if we are considering AC circuits that have inductance or capacitance reactance then current consumption will increase as voltage decreases.
Item #5 ? if 80vac isn?t within its operating range and it is a reactive load it will go into high current consumption - possibly causing the appliance damage.
Item #6 ? some very good question and food for the thought. I bet that a mis-calibrated meter rips us off more then anything else.
Item #7 - not likely. PF correction has only recently enter the consumer electronics market.
If the meter measures REAL power then I have erred and my answer is WRONG with respect to an increase in your bill. However the meters used here are designed for 120vac and calibrated for that voltage. It would be interesting to find out how the meter?s calibration (accuracy) is affected by a decrease in line voltage.
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Never said I?m an injunier :classic: but now I understand why the lights go dim when the generator goes offline and EDENORTE goes online, why my fan goes slower and why the microwave needs 20min to pop my popcorn rather then the 6min it used with the generator and why the toaster doesn?t brown my bread, unless I leave it much longer. They are doing less work (obviously) but I get to pay more for that? :classic: Wait a minute, now I?ve got it. It was the toaster that gave it away. I let the microwave and the toaster run longer, until the bread is brown, that?s why I pay more, right? But I still don?t see why the fan, which runs slower now, makes me pay more for it but doesn?t give me the same cooling effect.
As Mondongo said, it?s the meter that counts in this equation. Most meters that we use are meant to count the resistive currant component of the load. At least that?s how it used to be. I don?t know about the meters that EDENORTE is using, which are digital. A motor will use more amps then the meter is registering. That has something to do with inductance. That, btw, is the reason why in Germany you have to install capacitors into fluorescent lights. I always wondered why they don?t demand it in Toronto, considering all the office buildings that use only fluorescent lights.
As Mondongo said, it?s the meter that counts in this equation. Most meters that we use are meant to count the resistive currant component of the load. At least that?s how it used to be. I don?t know about the meters that EDENORTE is using, which are digital. A motor will use more amps then the meter is registering. That has something to do with inductance. That, btw, is the reason why in Germany you have to install capacitors into fluorescent lights. I always wondered why they don?t demand it in Toronto, considering all the office buildings that use only fluorescent lights.
kbf,
I'm in total agreement with you about a wood stove - especially Dominican style, which is basically an open fire on the top of a table.
Yes, I agree that every man deserves to have his food prepared that way - in a shack out back, of course, because of the smoke.
The gas stove should be only for emergencies when he has to do it himself.
I'm in total agreement with you about a wood stove - especially Dominican style, which is basically an open fire on the top of a table.
Yes, I agree that every man deserves to have his food prepared that way - in a shack out back, of course, because of the smoke.
The gas stove should be only for emergencies when he has to do it himself.
Well!!! It looks like I opened a bucket of worms, from the "discussion" I read about electricity!
Thanks to all you smart people out there, I have really learned a lot---I think???
I'll just have to get a few physics text books and study up some more.
All said and done, all of you who have contributed to the discussions are to be congratulated. You have done a real good job.
None of the above is presented with "tounge in cheek", but with all sincerity.
Thanks again.
Texas Bill
Thanks to all you smart people out there, I have really learned a lot---I think???
I'll just have to get a few physics text books and study up some more.
All said and done, all of you who have contributed to the discussions are to be congratulated. You have done a real good job.
None of the above is presented with "tounge in cheek", but with all sincerity.
Thanks again.
Texas Bill
Not being satisfied by the route this discussion has taken and because it behooves us ALL to know the real and true answer to this perplexing question, not to mention I hate to be wrong, I continued researching the original question as posed by Texas Bill. Much to the surprise of many, I was correct in my original assumption and partly for the reasons I stated previously. However there is more to the whole picture but my original stated premise is still very much valid. Unfortunately, our bill DOES INCREASE when line voltage is lower than the meter expects and for three reasons. I have already stated the first reason our bill increases (this is compounded by meter deficiency). The second reason has to do with the meter itself. The third and final reason is simpler in concept but less apparent and it has to do with what the electrical circuit requires to operate correctly and efficiently. Before addressing circuit efficiency I?ll quote the wattmeter theory of operation ? Skip pass it if you're not interested but be sure to read the quote on METER ERROR SOURCES.
Please notice the last sentence of item #3, ?Watthour meters read slightly high when voltage is low.? The lower the voltage the worst the 'slightly' becomes. This problem is aggravated by the fact that some of your appliances are consuming more current if they are reactive loads as previously discussed. Finally, the efficiency of fully resistive loads such as your iron, water heater, microwave and even your toaster will need to operate longer to get the job done. At first thought, and applying Ohm?s law on fully resistive loads, this doesn?t sound correct but in fact it is.
Let?s look at your 120vac water heater functioning with 80vac to understand the problem. For argument sake lets say you have a 1.5kw model water heater. You see when the voltage is lower your heater will draw lower current but for longer period of time and there is no guaranties that the heater will complete its task. Hence the water heater may NEVER turn off and be constantly drawing the lower current increasing your bill astronomically. Let?s apply Ohms law?
Ohm?s law for Power states:
P = I x E or P = (I^2) x R or P = (E^2) / R
Where P = power in watts, I = amps and E = voltage.
Note: ^ = ?to the power of?
Therefore (I^2) equals I squared.
Heater 120vac, 1500w (purely resistive load, Ohm?s law applies like in DC circuits)
Thermostat set for 186 degrees Fahrenheit
1500 / 120 = 12.5 amps are required to operate heater at 120vac.
Since the water heater is purely resistive 120vac will force 12.5 amps of current through the heating element of the heater. We can now find the resistive value of water heater using Ohm?s law again.
E = I x R or I = E / R or R = E / I
We need resistance = R therefore
R = 120 / 12.5
R = 9.6 ohms
At a line voltage of 80vac the water heater will consume 8.333 amps. (I = 80 / 9.6)
Using Ohm?s law for power (P = E x I) we arrive at 666.64 total watts used by the water heater a total reduction of almost 2/3 of its total working capacity or the water heater is only working at 44.44% of capacity. If it takes the water heater 30 minute to heat the water at 1500w it could take the water heater approximately 1 hour and 20 minutes to heat the water to the same temperature. In reality, however, the heating element will never get the water to 186 degrees Fahrenheit and the thermostat will NEVER turn off the heating element in the water heater. The current drain is lower but it will be FOR THE WHOLE MONTH - every last minute of it!!! Raising your bill by a considerable amount. As an exercises calculate what would be the temperature of the water in this water heater? If you set the thermostat on the water heater 1 degree below the value obtained from the previous calculation you will avoid this problem.
Please notice the last sentence of item #3, ?Watthour meters read slightly high when voltage is low.? The lower the voltage the worst the 'slightly' becomes. This problem is aggravated by the fact that some of your appliances are consuming more current if they are reactive loads as previously discussed. Finally, the efficiency of fully resistive loads such as your iron, water heater, microwave and even your toaster will need to operate longer to get the job done. At first thought, and applying Ohm?s law on fully resistive loads, this doesn?t sound correct but in fact it is.
Let?s look at your 120vac water heater functioning with 80vac to understand the problem. For argument sake lets say you have a 1.5kw model water heater. You see when the voltage is lower your heater will draw lower current but for longer period of time and there is no guaranties that the heater will complete its task. Hence the water heater may NEVER turn off and be constantly drawing the lower current increasing your bill astronomically. Let?s apply Ohms law?
Ohm?s law for Power states:
P = I x E or P = (I^2) x R or P = (E^2) / R
Where P = power in watts, I = amps and E = voltage.
Note: ^ = ?to the power of?
Therefore (I^2) equals I squared.
Heater 120vac, 1500w (purely resistive load, Ohm?s law applies like in DC circuits)
Thermostat set for 186 degrees Fahrenheit
1500 / 120 = 12.5 amps are required to operate heater at 120vac.
Since the water heater is purely resistive 120vac will force 12.5 amps of current through the heating element of the heater. We can now find the resistive value of water heater using Ohm?s law again.
E = I x R or I = E / R or R = E / I
We need resistance = R therefore
R = 120 / 12.5
R = 9.6 ohms
At a line voltage of 80vac the water heater will consume 8.333 amps. (I = 80 / 9.6)
Using Ohm?s law for power (P = E x I) we arrive at 666.64 total watts used by the water heater a total reduction of almost 2/3 of its total working capacity or the water heater is only working at 44.44% of capacity. If it takes the water heater 30 minute to heat the water at 1500w it could take the water heater approximately 1 hour and 20 minutes to heat the water to the same temperature. In reality, however, the heating element will never get the water to 186 degrees Fahrenheit and the thermostat will NEVER turn off the heating element in the water heater. The current drain is lower but it will be FOR THE WHOLE MONTH - every last minute of it!!! Raising your bill by a considerable amount. As an exercises calculate what would be the temperature of the water in this water heater? If you set the thermostat on the water heater 1 degree below the value obtained from the previous calculation you will avoid this problem.
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NotLurking....I appreciate your posts...so dont take my usual brusque manner personally.
Maxwell does NOT have a law named after him. What Maxwell did was modify Gauss', Ampere, and Faraday's laws and turn them from static electromagnetic equations to propagating electrodynamic equations. Maxwell was able to add time varying components to Ampere and Faradays's equations and solve the two to described travelling electro-magnetic waves.
Your second point: this is not correct. Of course AC circuits carry DC components. What you are confusing is the fact you cannot impress a DC voltage on an inductive component and you cannot impress a DC current source on a capacitve component. Inductors can carry currents and capacitors can carry voltage. What you mean to say is that the core of some inductors and transformers have properties that can change with increasing current. Transformers can saturate if you put too much current through them. If inductive elements cannot carry DC currents, how do you explain AC/DC converters? Your meter is an AC circuit. It carries the DC current that your house comsumes. This is not to be confused with the fact that the AC circuit itself does not DISSIPATE power, despite the fact it can carry or transfer it.
I will reply to you other post later. But first look at this link, it derives an exact equation for the energy consumption. What it tells you is that these meters DO measure energy. What it says if that if you use the same amount of power (VI), your meter WILL NOT charge you more. As the line voltage goes down, the line current goes up....net result no change. I hope there is no disagreement on this point.
http://www.public.iastate.edu/~dmumm/files/Webpage Format Files/Physics 222 Project.htm
This statement is invalid. The average of a periodic function is defined as its integral over its period. When you take an average, you have to define the function and its period, otherwise its a meaningless number.NotLurking said:
Your first point in this paragraph:NotLurking said:
Maxwell does NOT have a law named after him. What Maxwell did was modify Gauss', Ampere, and Faraday's laws and turn them from static electromagnetic equations to propagating electrodynamic equations. Maxwell was able to add time varying components to Ampere and Faradays's equations and solve the two to described travelling electro-magnetic waves.
Your second point: this is not correct. Of course AC circuits carry DC components. What you are confusing is the fact you cannot impress a DC voltage on an inductive component and you cannot impress a DC current source on a capacitve component. Inductors can carry currents and capacitors can carry voltage. What you mean to say is that the core of some inductors and transformers have properties that can change with increasing current. Transformers can saturate if you put too much current through them. If inductive elements cannot carry DC currents, how do you explain AC/DC converters? Your meter is an AC circuit. It carries the DC current that your house comsumes. This is not to be confused with the fact that the AC circuit itself does not DISSIPATE power, despite the fact it can carry or transfer it.
By definition, circuits that are comprised of inductors and capacitors only do not consume power!! In these circuits, energy just keeps getting transferred from magnetic to electric.NotLurking said:
I will reply to you other post later. But first look at this link, it derives an exact equation for the energy consumption. What it tells you is that these meters DO measure energy. What it says if that if you use the same amount of power (VI), your meter WILL NOT charge you more. As the line voltage goes down, the line current goes up....net result no change. I hope there is no disagreement on this point.
http://www.public.iastate.edu/~dmumm/files/Webpage Format Files/Physics 222 Project.htm
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