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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 earth pin in a 3-pin plug?
When you push the plug into the socket the earth pin engages a < gate which stops the live and neutral from being touched from the outside with any object other than the pins of the plug.
==thats the Answer == In US residential power connectors, the earth pin is longer to provide a return path before the hot pin engages. This way an appliance with a short to its case will simply trip a breaker instead of electrocuting the user. Ground Fault Interrupters provide additional protection by detecting an imbalance in the hot and neutral leads.
What is the current running through a resistor of 9 ohms with volts of 90?
I = E / R
If the voltage across the resistor is 90 volts, and the resistance of the resistor
is 9 ohms, then the current through the resistor is
90/9 = 10 Amperes.
Don't try this at home!
The power dissipated by the resistor is E2/R = (90)2/9 = 900 watts. That's comparable to the power (heat) dissipated by a small toaster. A common composition resistor will get hot and possibly explode if it's asked to dissipate that kind of power.
How does an ac generator work?
An ac generator works when the voltages appearing at the two wires alternates between positive and negative and then negative and positive each time when the magnet makes a complete revolution. An AC generator is a simple generator.
What type of oil is used for a 2006 Chevy Trailblazer EXT?
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How do the symbols of additive transformers differ from subtractive polarity?
Using North American standards, when terminal X1 is diagonally opposite terminal H1, the transformer is additive.
What is neutral to ground fault?
Neutral, by definition, is grounded at the distribution panel, and also at the distribution pole. That is how the hot to ground voltages are prevented from exceeding their normal voltage and encroaching on truly lethal voltages, such as 7.6kV in a typical US 13.2kV system, in a wye configuration.
Note: and this is critical, do not depend on the fact that neutral is grounded and consider that it is the same as protective earth ground. It is not. Protective earth ground is a different wire.
Can yo use a 19v dc power supply for a 6v dc load?
No. You can oversupply current - amperes (A) or milliamperes (mA) - because a device will only use the current it requires, but voltage should match exactly.
Voltage measures the amount of charge in a current (or, strictly, between two points in a circuit). If you oversupply your device's rated voltage you can burn it out. If you undersupply it, you'll either fail to power the device, or you can cause it to function incorrectly, which might or might not have permanent effects, depending on the device. The precise tolerance will vary from one device to another; try to match ratings exactly.
An overly simple metaphor for electric current is your home water supply. Voltage is like water pressure: it's a measure of the force with which current is provided. Current (amperage) is the rate of flow. Multiplied together, they determine total power (watts), which is like the amount of water provided.
As you open more faucets in your house, the total amount of water available to any single tap drops, and so does the rate of flow; but the pressure within the system can be externally regulated and remain the same. Likewise electricity: as you plug more devices into the wall, you consume more power, but the voltage remains constant because it's regulated. If you somehow raise the water pressure in your plumbing, you can overflow your bathtub, but providing more water at the same pressure just means that you can open more taps before any of them stop providing water.
Your household electricity is probably rated either from 110 VAC to 120 VAC, or from 220 VAC to 240 VAC. This remains the same no matter how many appliances you plug into the wall, and all of them must be designed for that voltage regardless of how much current they actually consume, alarm clock or microwave oven. The individual circuits in your house are usually rated at 15 or 20 amperes (A). This is a measure of the maximum current that they can supply, not of how much current they must supply. Each device has its own current needs, but all devices on the circuit run on the same voltage.
Whether it's AC or DC, any device has a certain current requirement at any given moment. If the voltage being supplied increases from 12V to 19V, that means that the total power delivery increases too, by a factor of just over 50%. It's as if you started forcing water through your pipes half again as fast: with 50% more water, your bathtub would have trouble keeping up. And so will your electronics.
ANSWER: Yes you can provided that an active device is installed in series to limit the voltage to 12 like LM7812. however a 12 volts source cannot be used on a 19 volts circuit because it may impair the circuitry
How does fluorescent tube glow?
A fluorescent lamp is a glass tube containing some mercury vapor, with a phosphorescent coating on the interior surface of the tube.
The mercury vapor is made to glow by using a high voltage across its electrodes that sets off an electric arc discharge in the tube. The discharge can also be described as a conducting plasma.
The resulting flow of current through the mercury vapor is stable and well-controlled by an external ballast, or loading device, which consists of a high-inductance choke-coil that is connected in series with the tube.
The continuing dischange glow is invisible to the human eye but it causes the phosphorescent coating on the interior surface of the tube to emit visible light.
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A fluorescent tube lamp works by using the fluorescence principle. It contains two filaments, one at each end of the tube, which glow to heat up the gas contained inside the tube.
The inner surface of the tube is coated with compound of elements having fluorescent properties, such as phosphorus. When it was manufactured all normal air was removed from the tube. In place of the air just a small trace of a gas is put into the tube, such as mercury vapor (for a white color), carbon dioxide (for green), neon (for red color), etc.
When the electrical supply is turned on, what happens is that the two filaments glow and then the contacts of the starter open. This action provides a voltage across the tube that is high enough to ionise the warmed-up gas inside the tube. This ionised gas, also called a "plasma", excites the special fluorescent coating on the inside of the tube so that it gives out visible light.
Note about the need for a choke and a starter
Without a high inductance choke in series with the tube, the plasma in the tube would simply short-out the service wires. That would always cause the circuit's protective fuse to blow - or its circuit breaker to trip - to cut off the supply of current to the tube. If that happened the tube light would never be able to perform its intended purpose, which is to continue running - and giving out a continuous light - for long periods of time.
The starter is a special kind of switch: its contacts are made of a metal alloy which, soon after a voltage is applied, heats up and bends, causing the switch contacts to open.
So a high-inductance choke must be used in circuit with the starter and the tube for two reasons:
- firstly the choke generates a high voltage pulse across the tube when the starter's contacts open. That pulse causes the gas in the tube to ionise and become a low-resistance plasma
and
- secondly, because it is wired in series with the tube, the choke greatly reduces the current drawn by the tube once it contains the low-resistance plasma.
For more information see the Related link below and the answers to the Related Questions.
What are the disadvantages of core and shell types construction?
The 'core' type is a magnetic circuit equivalent to an series electric circuit; a 'shell' type is equivalent to a parallel electric circuit. So, the reluctance (magnetic equivalent of resistance) will be lower for a shell type of similar cross-sectional
because it uses those cylenders weights which are called dead weights " aliving weight is any weight that could changr"
A conductor is simply a material that allows electrical energy to pass through it these tend to be metals or molten metal ions.
Where is the starter motor on a Peugeot 106?
The starter on a peugeot 106 is located at the back of the engine block on the right side. Very difficult to locate from above, since it is below the intake/airfilter equipment. From below it is easier. Take of the right front wheel and jack the car up or go underneath in a pit. There you will find the starter and one may see the electrcal connections to it. It is fastened with two bolts underneath (at the rear side of the starter and one on top going through the transmission block. On the diesel you need to remove the exhaust heat shield, and it will help to remove the exhaust front pipe - what a pain!
What are the disadvantages of Halogen Lamps?
They use too much electricity. In incandescent bulbs, a current is applied to a think wire that is called a filament. In fluorescent bulbs, a current is applied to a gas that fills the tube. There is no wire in a fluorescent tube. It's takes a lot less energy. LED lighting applies current directly to a semiconductive material which changes state without needing to get hot.
An incandescent bulb has a wire filament that heats up and glows when enough electricity passes through it. The length, thickness, and material of the filament determines how much light is given off by the filament, how much heat it generates, how much electric current it draws to emit that amount of light, and how long it lasts before burning out. Although Incandescent bulbs are considered inefficient because much of the electricity is converted to heat instead of just light, there are situations where the heat generated is also useful. Bakeries use commercial ovens with rows of many of these bulbs to generate the heat for baking. The bulbs are easily replaceable and cheaply available compared with electric ovens that use are forms of resistance wiring to create heat. In the winter such bulbs also help warm a home with radiant heat supplementing other forms of home heating.
Fluorescent bulbs are tubes with a mercury vapor. Since mercury is normally not a vapor at room temperature, the ends of the tube have a filament which heats up and glows when the lamp is turned on. The is enough to make mercury in the bulb vaporize. Electricity passing through the bulb then makes the mercury vapor generate ultraviolet light. The inside of the tube is coated with a material which when exposed to ultraviolet light generates visible light. This method is considered more efficient than an incandescent bulb as much less heat is generated. Fluorescent lamps are more expensive as additional parts are necessary to control the electricity to first heat the mercury to a vapor, switch off the filament, control the current going through the tube. Although fluorescent bulbs last longer than incandescent because it does not use a filament for light, each time it is turned on, it uses a filament which will eventually burn out.
An LED (Light Emitting Diode) is an electronic component called a diode that is constructed to emit light when electricity passes through it. The diode itself generates very little heat and theor is no filament to burn out so it has a very long lifetime.
The load is the product of the load current and the secondary voltage. So, in this example, the load is 8 x 2000 = 16 000 volt amperes, or 16 kVA. This must not exceed the transformer's rated kVA.
How does electric resistance relate to energy transformation?
Power in a circuit is inversely proportional to the resistance, all other things being equal.
Voltage equals amperes time resistances, so amperes equals voltage divided by resistance.
Watts equals voltage times amperes, so watts equals voltage squared divided by resistance.
What are the different types of torques?
There are various kinds of torques involved in opeartion of a motor:-
Starting Torque: At the starting, motor has to deal with standstiill condition, this torque should be good enough to deal with friction and windage
Load Torque: It is the torque which a motor faces on apply of load.
Breakdown Torque: more than this torque if more load is applied on a motor, torque generated will not increase and motor will starts slowing down
Why are power systems earthed or grounded?
Earthing is an important safety feature and most electrical appliances have a third earth wire separate from the two current-carrying wires, the live and neutral.
The earth wire is used to connect all the outer metal parts of all appliances to one common point which is also connected to the gas and water pipes and to an earth rod. That means that users will not receive a shock by touching different appliances, and it also prevents the build up of a static electric charge on equipment cases.
power= energy time the time in seconds power= energy time the time in seconds
How is a run capacitor constructed?
A run capacitor is constructed with wire, wire strippers, cling wrap, scissors, aluminum foil, and cellophane tape. A run capacitor is defined as a unit that stores energy electrostatically in an electric field.
While selecting an MCB you have to check: 1) Current Rating; 2) Response Time; 3) Manufacturer; 4) Type of MCB (means single pole, double pole, three pole, four pole - it depends on the application); 5) Cost; 6) short circuit breaking capacity. For more information see the answers to the Related Questions and the Related Link shown below.
What is the difference between transformer and generator and motor?
A motor is a machine that converts other forms of energy into mechanical energy, therefore creating motion.
A generator converts mechanical energy into electrical energy via the method of magnetic induction.
You should probably check up Michael Faraday and Lenz. Or maybe look in a HSC Year 12 text book like Jacaranda.
What is the difference between KW and KVAR?
kW is the unit of real power & kVA is the unit of Apparent power.
Apparent Power= real power + reactive power
Besides this,the ratings which we write on a motor or generator is KVA & not KW. B'coz there are two types of losses in a motor or generator- core losses & ohmic losses. Core loss depends upon the voltage applied & ohmic losses depend upon the current flowing & none of these losses depend upon the power factor i.e. Cos@. As we know that
KW power = V * I *Cos@.
But as the losses are independent of the power factor hence we need to calculate only KVA = V*I.
CommentApparent power is the vector sum of real power and reactive power, not the sum.
KVA is the unit of apparent power and KW is unit of active power.
KW is kilowatts, and KVA is kilovoltamps. KW is the apparent power that a normal power meter would measure, while KVA is simply the maximum of the instantaneous product of volts and amps divided by 1000. The difference between these two terms is due to phase angle, which is due to the reactance of the load to an AC power source.
KW (kilowatts) is apparant power, while KVA (kilovoltamps) is true power. They are different when the phase angle between voltage and current is not zero, i.e. when the load is reactive, such as in a motor. The ratio of KW over KVA is Power Factor, and is the cosine of the phase angle between voltage and current. It is zero at a phase angle of 90 degree, which occurs for purely (ideal) inductive or capacitive loads with no resistance in the source or conductors, and it is one for purely resistive loads.
How many advantages have parallel and series combinations of resistors?
There are so many advantage of parallel and series combination of resistors like if you need resistors with certain values and you have no resistors with enough values then you can create the one you need by connecting several parallel of those you have.
