How do I know if I have a 3-phase electrical supply at home?
While the other answers are all correct, there is another wrinkle you might want to be aware of.In general. household electrical service in North America is single phase three wire 120/240 volt. That is to say that there are three wires, two "hots" (typically red and black) and a "neutral" (typically white).If you measure the voltage between either of the hot wires and neutral, you will see about 120 volts. Between the two hots, it will be the sum of the voltages, or about 240 volts.In technical terms, the two hot wires are both 60 Hz alternating current, but they are 180 degrees out of phase.However...This is not always the case. There are some areas of the country where, for various reasons, there are some locations where single phase power is not easily available, but three phase power is. So, instead of using 120/240 single phase, they use two of the three phases.In those locations, the service you have coming into your house looks just the same. Two hots and a neutral. If you measure the voltage between either of the hot wires and neutral, you will see about 120 volts, just like in single phase service. But between the two hots, it will be about 208 volts, not 240.This is because the two hot wires are both 60 Hz alternating current, but instead of being 180 degrees out of phase, they are only 120 degrees out of phaseIn those locations, you can order water heaters, etc. for 208 volts instead of 240:
If the power supply voltage were doubled, how would the field pattern change? How about the potentials?
Field patterns don't change unless the geometry changes. Potentials are proportional to the source-sink differential. ... and the cow jumped over the moon.
A simple electrical circuit has a constant voltage power supply and a variable resistor as a circuit.?
As you increase the resistance the current flow B) Decreases
The output voltage of a power supply is normally distributed with a mean 5V and a stand dev of .02V. More...?
Firstly you need to equip yourself with a graph of a bell curve (probability curve). Through the peak of the bell draw a vertical line and lable it 5.00V If you are lucky then it already has the standard deviations marked on either side. Label these 4.8 and 5.2 V left then right. Now label the next two out from the center 4.6 and 5.4 and finally label the third std deviation at 4.4 and 5.6 V The area under the curve between 4.5 and 5.5 volts gives you the percentage of PSU's that will conform. All the area under the curve to the left of 4.5 and right of 5.5 are those that are failures. Now you would calculate the area with a difficult integration if kind people didn't have tables already created to tell you. So you see that the rejects are all those over 2.5 standard deviations away. From a handy table I can tell you that 2.5 std dev's represents 99.379% of products would be passed so that leaves 0.621% failures. Hope this helps Check out wikipedia entry on standard deviation, just ignore the calculus and you will find it not too bad.
What does an electricity company (mains) supply, exactly?
Let's get to fundamentals here. You're going to see a lot of answers talk about energy, voltage, current, power. But if you look at this properly, you'll find that fundamentally what's actually happening is that the power station is generating an electrical field. Electrical fields prefer to pervade objects high conductance (things like wires and such). This property of electrical fields allows us to extend the electrical field of the power station all the way to our homes using wires.The outlet on your wall is in fact one of the many end-points that this electrical field generated by the power stations on your electrical grid has been extended to. Connecting an appliance to that outlet is the act of connecting an appliance to this electrical field.Electrons are what both create, and are influenced by this electrical field. When an electron is placed in an electrical field, they will experience a force that causes them to move. This effect can be used to do all sorts of useful things ranging from heating, lighting, to digital electronics. When you connect your appliance to the outlet, the electrons in the circuitry of the appliance (and indeed, all the electrons in all the wires from you to the power station) move, and do whatever it is that the appliance is designed to do.You are paying for this electrical field. Voltage, or potential difference, is a measure of the strength of this field. Energy describes the ability of this field (and electrons within it) to do work. Power is the rate at which this happens.In other words: The power station supplies you with an electrical field, and charges you by the amount of work that the field does. Electrons are simply a carrier of this field, they're neither consumed nor lost, they just get moved around a bit (and in doing so manifest all the things we come to know as electricity).
High- voltage power supplies are sometimes designed intentionally to have larger internal resistance as a safe?
You can see from another answer that adding resistance to protect from electrical shock limits the current to a fraction of an amp. In electrical power distribution systems, a very small amount of inductive impedance is sometimes added to reduce the available fault current to a level that can more economically be protected by circuit breakers. A circuit breaker designed to safely clear a 10,000 amp fault is less expensive than a breaker with a higher interrupting capacity. In addition, limiting the fault current to 10,000 amps reduces the mechanical strength required to protect the conductor supporting structure from mechanical damage due to magnetic forces.
What is the capacitor voltage after this time?
The electrical energy stored in a capacitor is given by . A capacitor is charged through a resistor for a time equal to one time constant, from a power supply set to 10 V. What is the capacitor voltage after this time? What is the stored energy at this time, as a fraction of the maximum energy Emax, which can be stored in the capacitor?
What are feeders in power distribution? What is the voltage going through them? Why tapping is not taken from them?
Feeders are generally those voltage lines below 69kV. It really depends on the system but Transmission is higher voltage levels (in US that’s typically) 69kV up to 1,000kV lines intended for long distance transmission of power. 34.5kV and below is generally thought of as Distribution. It’s intended for local area distribution of electricity.The Voltage doesn’t ‘go through them’. Voltage is there ‘potential’. Current is what goes through them.I’m not sure exactly what ‘Why tapping is not taken from them?‘ is supposed to mean. I’m guessing you’re asking why don’t we have outlets that are connected directly too that live level voltage.There are several reasons.1.) Much higher probability of fire. With higher voltage levels a short to ground will result in a much higher current discharge and much more likely to start a fire.2.) For much the same reason as #1 the current through the human body if you become the conductor to ground is much more likely to kill you.3.) There’s not enough space and insulation between the wiring in a household circuits for this. The cost of wiring a household that would support this would not be feasibleThese are some of the reasons why we use transformers to bring the distribution line voltages down to use-able voltage levels (240/120 for homes - some industry may use 480v)