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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
What is the electrical voltage standard in the US?
120/240 volts at 60 cycles per second ac.
It is supplied as a single phase service, split 120V-0-120V.
One hot leg is 120 volts, a second hot leg 120 volts but running at 180 degrees out of phase from the first leg, and a neutral.
Every 120 volt outlet in your home carries one leg of 120 volts plus the neutral.
If the outlet has a ground, this is for safety in case there is a fault like a short of a hot leg to the internal frame or the outer casing of the appliance, which should always be connected to the ground. If such a fault occurs, the ground wire takes a very high current which causes the circuit breaker to trip or a fuse to blow.
An appliance such as a clothes dryer in your home, that uses 240 volts, is using both hot legs. Because they are 180 degrees out of phase from each other, the combined voltage is 240 volts.
For more information see the answer to the Related Question shown below.
What is the difference between 277 volts and 240 volts?
These voltages are both wye connection three phase voltages. The voltage difference comes from the primary three phase voltage supplies. 277 volts is obtained from 277 x 1.73 = 480 and 240 volts is obtained from 240 x 1.73 = 415. 480/277 volts is a common three phase American voltage. 415/240 volts is a European voltage. In Canada a common three phase voltage is 347/600. The 240 volts could also be a single phase voltage in North America derived from a split phase secondary on a distribution transformer that supplies 120/240 volts to homes.
Electrical energy absorbed by the lamp's filament produces thermal energy as well as light.
What is the lumen output of a 30W LED flood light?
Generally lumen is a measure of the total amount visible light form a lamp or light source. LEDs are about the same as CFLs, producing about 50 lumens per watt, compared to 10 lumens for incandescent bulbs or 13 lumens for halogen.
What is the difference between electric charge and ion?
An electric current goes through an electric circuit, if it is closed.
What is the realtionship among voltage current and resistance in a circuit?
Ohm's Law
Voltage = Current x Resistance
By Ohm's Law, current is voltage divided by resistance, so if you double both the voltage and the resistance, the current would remain the same.
Kilo means 1000. The prefix is used for measurements such as:
weight -- kilogram = 1000 grams
distance -- kilometer = 1000 meters
energy -- kilojoules = 1000 joules
You can buy a kilo of meat, a kilo of apples.
You can measure a person's weight, 80kilos.
As the breaker is tripped, a magnetic coil is beneath it and as the movable contact falls into the coil the arc is elongated in a spiral caused by the magnetic coil until the SF6 quenches the arc.
What are your current goals in your current position?
Im working as a receptionist,please I have no idea what are the goals to achieve for my possition for the next review period.. please give some a good answer ..
Why do you need fuses or circuit breakers?
If a fault occurs in a device, then it can cause high, dangerous currents. For instance, if the live of a household appliance comes into contact with the ground, then the resulting current could heat up wires and cause them to burn. Worse, if this connection to ground is made through the body then it can cause burns or even fibrillation.
If a high enough current must pass through a fuse, then the inside of the fuse melts and cuts off the current. The fuse must then be replaced. If a high enough current passes through a meter connected to a breaker, then the breaker is "tripped". This again cuts off the current, but the circuit can be re-made without replacing parts.
What type of resistance does a good insulator provide?
A perfect insulator (which does not really exist) would have an infinitely high resistance. Good insulators provide very high resistance to current flow, on the order of tens of megohms and up.
What is the cost to change fuse box to a circuit breaker?
Hire an electrician. The fuse box is the main distribution point of your elecrical system. If installed wrong it will set your house on fire. It will be inspected when you sell your home and if you do it wrong the inspector will force you to have it fixed by a professional. This is not worth trying to do it yourself. There is to much at stake and too many people will be watching (Don't forget you will have to notify the power company to shut your power off, so you can't fly "under the radar".) If you mess up grounding or switch a wire it will make every electrical device in your house unsafe. This is a big job, and not one for someone inexperienced. Finally, I will add do it right or don't do it at all. If you are negligent you could easily kill someone through fire or electrocution. If you read and do your homework and learn what it required you may find that small electrical repairs can be quick and easy. If you can't understand what you need to do hire an electrician. The cost of a professional is not worth the time you will waste if you don't understand what you are doing and the danger therein. This is not a small job, this is a major rework of the heart of your home electrical system. Hire a professional. If you are looking to convert your box simply for the convenience of flippng a switch when you blow a circuit, you can always choose to use a minibreaker, which is a eddison-type that can be reset with the push of a button. This often is a more cost effective solution.
when 2 different cpnducting materials r brought together and given a supply, there exist a potential difference between the 2.since these are 2 differt materials and an emf will be induced which is called thermo emf
What is the working principle of the drink dispenser?
It operates over a thermal cycle where a gas (like freon) is passed through a compressor and thus becomes hot.This gas then condeses to a liquid as it heats the water container.The condensed liquid again passes through an evapourator and becomes gas again & comes to the compressor to start the process again.
You really should be asking what is 'line' and neutral.
In Europe, the secondary winding of a distribution transformer has a pair of terminals. One is connected to earth and, therefore, has a potential of approximately 0 V with respect to earth. This terminal is termed the neutral, and the conductor connected to this terminal is called the neutral conductor. The other terminal is termed the line, and the conductor connected to this terminal is called the line (not 'phase'!) conductor. A distribution transformer's line conductor has a nominal potential of 230 V with respect to the neutral.
In North America, distribution transformers' secondary windings have three terminals. The centre terminal is grounded, and provides the neutral. Each of the outer terminals acts as a line terminal. The nominal potential difference between each of these two line terminals is 240 V, while the nominal potential between either line terminal and the neutral terminal is 120 V.
How do you connect a shunt resistor to a DC circuit to measure current?
To measure the current in a DC circuit an ammeter may be used. This ammeter may consist of a sensitive meter with a shunt in parallel with it to divert part of the current. In case even more current is expected than the full scale reading of the meter an additional shunt may be connected in parallel with that arrangement.
Are ammeters connected in series with the circuit under test?
Ammeters are connected in series with the circuit under test. Even the clamp on ammeter is a series device, taking advantage of the fact that the conductor is a half turn transformer winding that you can measure the current through.
How does load current vary with the load resistance?
Their relationship is only dependent on the voltage lost across that resistor; voltage equals resistance times current, so increasing the current for a given voltage will require a decrease in the resistance, and vice versa.
What is needed for electromagnetic induction?
An electric current is produced by the change in Magnetic flux over time
Read more: How_do_electromagnets_work
i think it is symbolised with a capital 'e' or 'v' :P hope this helped! :L:L
What is the principle of a three-phase induction motor?
An electric motor converts electrical energy into a mechanical energy which is then supplied to different types of loads. A.c. motors operate on an a.c. supply, and they are classified into synchronous, single phase and 3 phase induction, and special purpose motors. Out of all types, 3 phase induction motors are most widely used for industrial applications mainly because they do not require a starting device.
A 3 phase induction motor derives its name from the fact that the rotor current is induced by the magnetic field, instead of electrical connections.
The operating principle of a 3 phase induction motor is based on the production of r.m.f.
What is the procedure to polarity test a 3 phase transformer?
A 'polarity test' is conducted on a single-phase transformer, not a three-phase transformer (or transformer bank). The polarity of a single-phase transformer being important if two transformers are to be connected in parallel, or three transformers are going to be connected to form a three-phase transformer bank.
'Angular displacement' is, to a three-phase transformer, what 'polarity' is to a single-phase transformer. So you really should be asking about angular displacement, rather than polarity. Angular displacement, or 'phase displacement', is the angle by which the secondary line voltage lags the primary line voltage.
Angular displacement can be determined either by drawing a phasor diagram of the three-phase connection and measuring it, or by looking up the connection in a vector-group chart/table -you would nor normally 'calculate' angular displacement.
