Electrical Engineering

Your question should read, 'How much clearance is needed between LINES.... (not 'phases')?' The answer will depend on local authority regulations. The clearances in air tolerated by REC companies in the UK is 90 mm line to line and 127mm phase to earth. Even though there is a greater potential difference between line to line, the gap is less. I think it's to do with public safety if it flashes to earth.

Any load would do or anything that has resistance. Which is pretty much everything you can hook up to a circuit. For example, lightbulb, buzzer, resistor etc.

To Step down high voltages we require CVT,because it will step down the volatge by uisng capacitor in its circuit.

Connect one end of a piece of wire to a battery terminal and the other end to the other terminal. The ends of the wire become oppositely charged and the electrons in the wire flow along it towards the positive terminal. This causes the chemicals in the battery to change and eventually they will all be changed and the battery will be flat. It will then be unable to keep the ends of the wire oppositely charged and the current will stop.

Or you could connect the wire to the terminals of a generator. The laws of magnetism will cause the generator - when it's turned - to charge the ends of the wire oppositely and a current will flow. But only while the generator is turning, because as soon as the electrons move down the wire they neutralise the charge, which must be replaced to keep the current flowing.

In a simple parallel circuit -- for example, two resistors in parallel with a voltage source -- the voltage across the terminals of each component is the same. The current, however, 'splits' in order to take the two separate paths. In this case, you would use Ohm's law to find the current through each branch. In other words:

I1=V/R1, I2=V/R2.

If you have a current source instead of a voltage source, you would use current division to calculate current:

I1=Isource*R2/(R1+R2), and I2=Isource*R1/(R1+R2).

This is all in contrast with a simple series circuit, in which the current is the same through each component but the voltage drops are different. In which case you would use Ohm's law or Voltage division to calculate the individual voltages, depending on the source.

A lot, depending on the type of application and the strength of the body.

Series circuits, I'm doing my junior cert science so this may be wrong, but I'm pretty sure an example would be Christmas lights.

If one blows they all are extinguished, because they share the one current of electricity.

Car lights are parallel circuits....

I can't think of another series one, but I hope I helped a bit.

Digital Multimeter - Principles of Operation 1. To understand a digital multimeter, it is helpful to consider its analog progenitor first. An analog multimeter has a core function of current-to-display conversion: a current through the coil of a d'Arsonval movement creates a magnetic field that deflects a rotating, pivoted permanent magnet with an attached needle and a restoring spring. Needle deflection is proportional to the current. The range of applied currents is very narrow, such as 0‑50 microamperes, and is adjusted to the signal under test by building a resistor network inside the meter box and choosing the combination to be used for each scale with a switch of some type. See Figure 1. Overall accuracy is directly proportional to the accuracy of the resistors. For resistance testing, a battery inside the box provides a current source, and the needle is zeroed by shorting the test leads together and adjusting a built-in series potentiometer until the needle reads zero ohms (actually set to full scale). Adding the resistor under test reduces the current, in a logarithmic way that can be read on a reversed (zero on the right) and very nonlinear scale. Accuracy is best at midscale so several scales are provided. For AC measurements, a diode provides rectification, the scale is adjusted to give approximate RMS readings, and capacitance may be inserted to improve accuracy over a range of frequencies. 2. A digital multimeter is essentially a voltage-to-display device, instead. The scaling resistor network and its selector switch(es) may be the same or similar. Because a voltage difference between two input terminals is measured, the meter will have a differential amplifier (diff amp) front end that operates over a range and shifts an input signal into a range and DC offset compatible with an analog-to-digital converter (ADC) that most often has a multiple-digit decimal output. Almost any ADC for DMM use has at least an overrange indication and can indicate whether the differential input signal is positive (the "positive" input terminal, as arbitrarily assigned, is more positive than the "negative" ditto for a "positive" input signal) or negative (the opposite). The number of digits reflects the internal precision of the ADC and the intended price point for the DMM to be built with it---more digits in the display means more cost to build. Conversion rates are usually slow: people can only see a few new digital values per second, and speed costs in terms of power consumption. If the range is manually set, there is a decimal point before and/or after each digit, and the switch turns on the correct one for the range in use. 3. Selecting voltage, current, resistance, power, etc. is done by the switches. For current, many meters (digital and analog) provide another set of inputs to plug the test leads into. This is meant to remind you that you're about to try to blow up the meter. Most meters have a shunt with a fraction of an ohm of resistance, measure the voltage across that, and display it as current. Some meters have a fuse in series with the ammeter shunt, to take the meter off line and remind you to be more careful. The same applies to extreme voltage measurements, which can exceed the range of the diff amp circuit and can be physically hazardous. 4. Auto-ranging adds complexity and convenience. There is already an overrange signal; this can be routed to the diff amp, if it has some processing power, or kept inside the ADC, if it has switch control line outputs. In both cases, the overrange signal causes electronic switches (relays, FETs, etc.) to be turned on and off to decrease the gain of the diff amp by a factor of ten. Since whatever goes up must come down, auto-ranging also needs an underrange signal---if the most significant digit is a zero, set underrange to TRUE and adjust the gain up by a factor of ten. Wait for stability (a few consecutive readings are the same). Adjust again if needed. 5. Note that there are 3- and 4-digit (and more) DMMs, plus 3-1/2, 3-3/4, 4-1/2, etc. The existence of the strange ones reflects historic cost considerations, but is now well established. A 3-1/2 digit meter reads 000-999 plus 1000 to 1999. Since this is twice as high as a 3-digit meter can read, it is arbitrarily called a 3-1/2 digit. A seven-segment display for this only needs the two segments that make up a "1" to perform this function. A 3-3/4 digit meter reads 000-3999, doubling the range again, but saving only one segment compared to a full 4-digit display. One could define a 3-7/8 digit meter as extending to 7999, and use a regular 4-digit display, but this is not normally done, since you are practically at the next level but probably have to charge less for it.

What is the definition of voltmeter-ammeter method?

== == == == It's a receptacle symbol, usually with "GFCI", "G", or "GFI" written under it. To find out exactly which symbol is used on your prints, look at the electrical legend, which is normally page E-1, E-001, etc.

Specific resistivity is directly proportional to area of cross section of the conductor and specific conductivity is the inverse of specific resistivity. So we can say , Specific conductivity is directly proportional to area of cross section of the conductor.

The slip measures the percentage by which the actual speed is less than the synchronous speed.

AC motors have a synchronous speed of 3000 rpm on a 50 Hz system, or 3600 rpm on 50 Hz. Some motors might have a synchronous speed half or a third of those speeds (or less), because the synchronous speed must be divided by the number of pole-pairs.

For a 50 Hz motor running at 2850 rpm the slip is (3000-2850)/3000 or 5%. The slip speed is 2850 rpm.

A negative DC source could be connected in such a way as to act as a positive DC source. I'm not sure why you would want to flip it - supplying power "the wrong way" could cause equipment failures, protective systems (such as fusing) to not provide protection, and general other bad things.

Claims about perpetual motion machines are always false because they ignore the inevitable losses of energy which must be overcome to make any machine operate so that it can do its intended work. Such losses mean that any machine, whether electrical or mechanical, must be supplied with more input power than it can convert into output power.

In the case of electrical machines there are many reasons for energy losses:

Bearing friction losses; "windage" losses caused by air having to be moved out of the way by spinning parts such as rotating armatures and cooling fans; magnetic hysteresis losses absorbed by eddy currents flowing in rotor armature and stator laminations; commutation losses in dc machines and slip ring losses in ac machines; excitation losses caused by the need to supply energy to the coils in the stator of a machine in order to magnetize it; general electrical resistance losses caused by the need to use energy to force electric currents to flow through the windings of any electrical machine.

Whilst engineers have found ways to reduce each one of those types of loss to a minimum, it is still a fact of life that no electrical machine can be 100% efficient. In the case of a motor, it will always require more energy to be supplied to it than it can convert to mechanical power. In the case of a generator, it will always require more mechanical power to be supplied to it than it can generate as electricity.

Some electrical machines have a power-conversion efficiency of up to 80% but most have efficiencies much less than that. If a motor and a generator were linked together to form a motor-generator set (the motor driving the generator driving the same motor) then, if both machines were as good as 80% efficient, that would mean the combined efficiency of the system of would only be .8 x .8 = .64 i.e. 64%. In other words, to keep the motor-generator set running, additional power equal to at least 36% of the motor-generator set system's own power would need to be supplied from an external source.

Those facts make the set-up described in the answer to this question shown below pure nonsense. Period.

"How does increasing the voltage in a circuit affect the energy of the electrons flowing in the current?" Answer: The charge of an electron is constant. Every electron has a charge of something like 1.6 x 10^-19 coulombs. (The mass of an electron is also constant which will be important below). When the current in a simple direct-current electrical circuit is 1.0 Ampere there are 6.25 X 10^+18 electrons/second (or 1.0 coulomb of charge) flowing past a given point in the circuit (this is by definition or convention). The voltage (V) is equal to the current (I) times the resistance (R), or V=IR. So, in a simple direct current circuit where the resistance is constant (we will just assume that for the sake of simplicity), if we increase the voltage, the current must increase proportionately. This means the total charge passing a given point in the circuit must increase. This means that more electrons must pass a given point in the curcuit every second. Since the charge of every individual electron is constant there must be more electrons moving past a given point every second.What actually happens to the energy of the electrons flowing in the circuit depends on the geometry of the circuit. If the electrons are forced to travel in single-file (like cars on a one lane road), then in order for more of them to pass a given point every second, their velocity must increase. In this case, their energy would also increase according to the formula for kinetic energy (KE) of a moving particle KE=1/2MV^+2 (or one half the mass (M) times the velocity (V) squared). (This is where we have to remember that electrons are particles with constant mass too.) In this case, the energy increases with the square of the velocity of the moving electrons. However, if the electrons still travel at the same speed but on different paths (like cars on a multi-lane highway) so that more of them can get past a given point every second, then their energy doesn't change. In reality the resistance (R) also generally increases with an increase in voltage (V) so the current (I) may not increase in direct proportion to the voltage but the current will generally increase until too much heat and resistance occurs. The heat generated by such a circuit is proportional to the square of the current which is pretty dramatic.

an electrical charge is measured in Coulombs, which is equal one ampere-second. That is, one ampere of current through a plane is equivalent to one coulomb of charge passing through the plane per second.
Current

It easy.We know p=vi.So just put the value in the equation.

the ratio of the relative speed of stator magnetic field with the speed of rotor, to the speed of rotor is defined as slip.

where as in torque slip characteristic is the graph between the speed of the rotor and the torque experienced on the rotor.

in the case of induction motor, the torque decreases with the increase in the rotors speed.

while in the case of sychronous motor, its different (you check out, because i just forgot about it!!

keep smiling!

Yes, most VFDs can run faster than the input power frequency so you can run a motor to 60Hz with a 50Hz power source. Just be aware that as speed increases, so will the current. Also be aware that a motor is rated to run a specific rpm and running faster may cause motor bearing failure after a short time.

any factor which produce motion in a body or tends to move the body..

Not only move the body but also make it change its direction or even its geometry. For instance, if you trip while running, you'll fall, and so your direction will be changed. If you press too hard, you'll smash an egg, so you've just altered the egg's geometry. These are two basic examples.