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Electrical Engineering
Electrical engineering is a field of engineering that deals with the study and application of electricity, electronics and electromagnetism.
23,056 Questions
Do 110 to 220 voltage converters work?
Sure, it is a very common converter and you will find plenty of vendors in the web.
What will be the current reading on the ammeter?
You measure the amount of volts(I) going through whatever you attached it to
What is input impedance of amplifier?
Basically, measure the input voltage and current, output voltage and current, and apply Ohm's Law.
Practically, you can apply a signal to an amplifier and measure its output. Then place a variable series resistor between the signal generator and adjust the resistor until the output drops to 50%. The resistor's value is the amp's input impedance, Zin.
While this will work OK at DC and audio frequencies, once you get to some hundreds of kilohertz and higher, you will need specialist equipment to measure Zin.
You might expect that you can put a variable resistor on the output and adjust the resistor until you get 50% of output. This will work with low-power amplifiers with substantial Zout.
Most audio amplifiers have *very low* Zout (less than an ohm), so trying this will probably blow the amplifier. You will need special test gear for (i) audio power amplifiers, even those in portable equipment, and (ii) anything above a few hundred kilohertz, as for Zin.
Who do the electricity at work regulations apply to?
The Electricity at Work Regulations (1989) are intended to control the risks arising from the use of electricity at work. All those places of work covered by the Health and Safety at Work Act(shops, offices, factories,workshops, farms, garages, etc.) are also covered under these Regulations.
The Regulations specify that responsibility for safety rests with the 'duty holder', who may be an employer, or a self-employed person who employs one or more individuals under a contract of employment. This 'duty holder' has a responsibility to assess those work activities which utilises electricity, or which may be affected by it.
What is windage loss of motor?
Windage loss is essentially frictional losses acting on rotating members due to air resistance.
Is mica an electrical insulator?
Mica has such poor electrical conductivity that it has often been used as an insulator. The resistivity of mica ranges from 1x10^12 to 2x10^14 Ω/cm depending on the type of mica. For reference, copper, a good conductor, has a resistivity of only 1.68×10^−8 Ω/m or 1.68x10^-10 Ω/cm.
no, it is an insulator.
What would be the total voltage in a circuit that has two 6 volt batteries connected in series?
4 amperes.
The voltage adds when batteries are connected in series. If they are the same voltage then the voltage doubles. Using Ohm's law: V = I*R with the voltage doubling and resistance being the same you get I = 2V/R and where V/R was your initial current you get I = 2*2ampers = 4 ampreres
How did the Singer sewing machine of 1851 work?
Howe was not the first to conceive of the idea of a sewing machine. Many other people had formulated the idea of such a machine before him, one as early as 1790, and some had even patented their designs and produced working machines, in one case at least 80 of them. However, Howe originated significant refinements to the design concepts of his predecessors, and on September 10, 1846, he was awarded the first United States patent (U.S. Patent 4,750) for a sewing machine using a lockstitch design. His machine contained the three essential features common to most modern machines:
a needle with the eye at the point,
a shuttle operating beneath the cloth to form the lock stitch, and
an automatic feed.
Despite securing his patent, Howe had considerable difficulty finding investors in the United States to finance production of his invention, so his elder brother Amasa Bemis Howe traveled to England in October 1846 to seek financing. Amasa was able to sell his first machine for £250 to William Thomas of Cheapside, London, who owned a factory for the manufacture of corsets, umbrellas and valises. Elias and his family joined Amasa in London in 1848, but after business disputes with Thomas and failing health of his wife, Howe returned nearly penniless to the United States. His wife Elizabeth, who preceded Elias back to the United States, died in Cambridge, Massachusetts shortly after his return in 1849.
Despite his efforts to sell his machine, other entrepreneurs began manufacturing sewing machines. Howe was forced to defend his patent in a court case that lasted from 1849 to 1854 because he found that Isaac Singer with cooperation from Walter Hunt had perfected a facsimile of his machine and was selling it with the same lockstitch that Howe had invented and patented. He won the dispute and earned considerable royalties from Singer and others for sales of his invention. Howe contributed much of the money he earned to the equip the 17th Connecticut Volunteer Infantry Regiment of the Union Army during the Civil War, in which Howe served during the Civil War as a private in Company D and regimental postmaster from August 14, 1862, to July 19, 1865.
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What is difference between voltage and emf?
An electromotive force (e.m.f.) is the open-circuit, or no-load, potential difference provided by a source -such as a battery or generator. For a closed circuit, an e.m.f. is the sum of the voltage-drops around any closed loop, including the internal voltage drop of the source.
A potential difference (voltage) can exist across any circuit component. For example, the fact that current is flowing through each of several resistors in a series circuit means that there must be an individual potential difference across each of those resistors (which we also term 'voltage drop').
An electromotive force is the name we give to the open-circuit potential difference provided by a generator, battery, etc. For example, the open circuit potential difference of a battery would be its electromotive force.
So, if we use a series resistive circuit as an example, the battery would provide the electromotive force, while voltage drops would then appear across its internal resistance, and across each of the resistances. The magnitude of the electromotive force is then equal (but acting in the opposite sense) to the sum of the voltage drops, including the internal voltage drop.
Many textbooks use the symbol, E, to represent an electromotive force, and V to represent potential difference. So, Kirchhoff's Voltage Law, for example, will often be seen written as: E = V1 + V2 + V3 + etc.
How do you convert 220 volts 50 Hz to 110 volts 60 Hz?
Converting the voltage isn't a problem, but converting the frequency could require some additional support electronics.
To convert 220 volts to 110 volts, all you need is a transformer with a 220 volt primary and a 110 volt secondary.
To convert the frequency, you'd need to come up with either a frequency converter or design and build one.
What is an air blast circuit breaker and how its operate?
The circuit breaker is an absolutely essential device in the modern world, and one of the most important safety mechanisms in your home. Whenever electrical wiring in a building has too much current flowing through it, these simple machines cut the power until somebody can fix the problem. Without circuit breakers (or the alternative, fuses), household electricity would be impractical because of the potential for fires and other mayhem resulting from simple wiring problems and equipment failures.
In this article, we'll find out how circuit breakers and fuses monitor electrical current and how they cut off the power when current levels get too high. As we'll see, the circuit breaker is an incredibly simple solution to a potentially deadly problem.
To understand circuit breakers, it helps to know how household electricity works.
Electricity is defined by three major attributes:
- Voltage
- Current
- Resistance
Voltage is the "pressure" that makes an electric charge move. Current is the charge's "flow" -- the rate at which the charge moves through the conductor, measured at any particular point. The conductor offers a certain amount of resistanceto this flow, which varies depending on the conductor's composition and size.
Voltage, current and resistance are all interrelated -- you can't change one without changing another. Current is equal to voltage divided by resistance (commonly written as I = v / r). This makes intuitive sense: If you increase the pressure working on electric charge or decrease the resistance, more charge will flow. If you decrease pressure or increase resistance, less charge will flow. To learn more, check out How Electricity Works. Circuit Breaker: At Work in Your HomeThe power distribution grid delivers electricity from a power plant to your house. Inside your house, the electric charge moves in a large circuit, which is composed of many smaller circuits. One end of the circuit, the hot wire, leads to the power plant. The other end, called the neutral wire, leads to ground. Because the hot wire connects to a high energy source, and the neutral wire connects to an electrically neutral source (the earth), there is a voltage across the circuit -- charge moves whenever the circuit is closed. The current is said to be alternating current, because it rapidly changes direction. (See How Power Distribution Grids Work for more information.)
The power distribution grid delivers electricity at a consistent voltage (120 and 240 volts in the United States), but resistance (and therefore current) varies in a house. All of the different light bulbs and electrical appliances offer a certain amount of resistance, also described as the load. This resistance is what makes the appliance work. A light bulb, for example, has a filament inside that is very resistant to flowing charge. The charge has to work hard to move along, which heats up the filament, causing it to glow.
In building wiring, the hot wire and the neutral wire never touch directly. The charge running through the circuit always passes through an appliance, which acts as a resistor. In this way, the electrical resistance in appliances limits how much charge can flow through a circuit (with a constant voltage and a constant resistance, the current must also be constant). Appliances are designed to keep current at a relatively low level for safety purposes. Too much charge flowing through a circuit at a particular time would heat the appliance's wires and the building's wiring to unsafe levels, possibly causing a fire.
This keeps the electrical system running smoothly most of the time. But occasionally, something will connect the hot wire directly to the neutral wire or something else leading to ground. For example, a fan motor might overheat and melt, fusing the hot and neutral wires together. Or someone might drive a nail into the wall, accidentally puncturing one of the power lines. When the hot wire is connected directly to ground, there is minimal resistance in the circuit, so the voltage pushes a huge amount of charge through the wire. If this continues, the wires can overheat and start a fire.
The circuit breaker's job is to cut off the circuit whenever the current jumps above a safe level. In the following sections, we'll find out how it does this.
Breaker Design: BasicThe simplest circuit protection device is the fuse. A fuse is just a thin wire, enclosed in a casing, that plugs into the circuit. When a circuit is closed, all charge flows through the fuse wire -- the fuse experiences the same current as any other point along the circuit. The fuse is designed to disintegrate when it heats up above a certain level -- if the current climbs too high, it burns up the wire. Destroying the fuse opens the circuit before the excess current can damage the building wiring.
The problem with fuses is they only work once. Every time you blow a fuse, you have to replace it with a new one. A circuit breaker does the same thing as a fuse -- it opens a circuit as soon as current climbs to unsafe levels -- but you can use it over and over again.
The basic circuit breaker consists of a simple switch, connected to either a bimetallic strip or an electromagnet. The diagram below shows a typical electromagnet design.
The hot wire in the circuit connects to the two ends of the switch. When the switch is flipped to the on position, electricity can flow from the bottom terminal, through the electromagnet, up to the moving contact, across to the stationary contact and out to the upper terminal.
The electricity magnetizes the electromagnet (See How Electromagnets Work to find out why). Increasing current boosts the electromagnet's magnetic force, and decreasing current lowers the magnetism. When the current jumps to unsafe levels, the electromagnet is strong enough to pull down a metal lever connected to the switch linkage. The entire linkage shifts, tilting the moving contact away from the stationary contact to break the circuit. The electricity shuts off.
Click on the circuit breaker to release the switch.A bimetallic strip design works on the same principle, except that instead of energizing an electromagnet, the high current bends a thin strip to move the linkage. Some circuit breakers use an explosive charge to throw the switch. When current rises above a certain level, it ignites explosive material, which drives a piston to open the switch.Power Systems or Transmission & Distribution
What is the total resistance in a parrellel ciruit?
The rule for finding total resistance in a parallel circuit is that a parallel circuit has two or more paths for current to flow through. Another rule states that voltage is the same across each component of the parallel circuit. If one of the parallel paths is broken, current will still continue to flow in all the other paths.
What is the 3 advantages of parallel circuit over a series circuit?
The advantages of parallel circuits are that if one component, e.g. light bulb fails, the other ones will keep functioning. The problem with series circuits are that if one light bulb fails, the others are also affected.
How star delta helping motor from overheat?
star delta motors start as a Y for 3 phase so the windings that normally see 480 volts see 277V a relay switches to delta then it runs as a normal delta motor
the reduces the starting current by about 60% for 3 phase
How long does a run capacitor last?
Start or run capacitor? How often does the motor cycle on and off? The biggest enemy of capacitors is heat. If the unit is outside in the summer heat, it's lifetime is much shorter than one inside where the temp is conditioned. So, depending on the factors above, the answer could range anywhere from as short as a year to ten years or more.
What is amplitude modulation and frequency modulation and difference between them?
Both angle and amplitude modulation are involved in radio wavelength patterns. Angle modulation is where the modulating wave manipulates the angle of a sine-wave carrier. The two types of angle modulation include frequency and phase modulation. On the other hand, Amplitude modulation is the strength behind carrying the waveform in radio.
What is the difference between sheathed and non-sheathed cable?
Cable sheath current is a current induced in the sheath by radio, magnetic or other interference, or a fault condition. The cable sheath should be grounded at one end so that this current flows to ground safely.
Iron losses (Pi) are independent of of load which occur due to pulsation of flux in the core.
Iron losses include both Hysteresis loss and eddy current loss and is same at all the loads.
Why does capacitor banks explode?
electrolytic capacitors will explode if installed backwards. it has to do with their being polarized and when reverse polarized their dielectric is destroyed and the resulting large current flow causes rapid generation of hydrogen gas, bursting the case.
The Power Factor is an indicator of the quality of design and management of an electrical installation. It relies on two very basic notions: active and apparent power.
The active power P (kW) is the real power transmitted to loads such as motors, lamps, heaters, and computers. The electrical active power is transformed into mechanical power, heat or light.
In a circuit where the applied r.m.s. voltage is Vrms and the circulating r.m.s. current is Irms, the apparent power S (kVA) is the product: Vrms x Irms.
The apparent power is the basis for electrical equipment rating.
The Power Factor λ is the ratio of the active power P (kW) to the apparent power S (kVA):
The load may be a single power-consuming item, or a number of items (for example an entire installation).
The value of power factor will range from 0 to 1.
How do you wire a single phase motor to go forward and reverse?
THIS IS ALSO KNOWN AS DRUM SWITCH. JUST PURCHASE NEW ONE AND YOU WILL FIND IT AS USER FRIENDLY--- IT HAS FULLY LABELLED TERMINALS FOR INPUT AND OUTPUT CABLES AND THE MECHANISM WILL DO THE WORK EITHER REVERSE OR FORWARD ROTATION AND WITH A CENTER-OFF FUNCTION.
What is the incoming voltage from the current source to the transformer called?
the incoming voltage from the current source to the transformer is called primary voltage.....
