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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
When resistance decreases what happens to current?
Based on the simplest Electrical Equation V = I * R,
(reads: voltage equals current multiplied by resistance)
then, rearranged I = V / R .
As resistance decreases, current flow proportionately increases
Why the efficiency of induction motor is less than that of transformer?
Because, the losses of IM is more due to the contribution of friction losses at shaft bearings and wind age losses in rotor air gap, this reduces the efficiency of the equipment, Since transforms is a static equipment zero mechanical loss so efficiency of the equipments in high .
How do you repair a laptop after spilling nail polish remover on it?
You could try using nail polish remover, and if it doesn't work try a damp cloth not to damp and rub it gently on the area.
Why do people working on electronic equipment wear wrist straps that connect them to the equipment?
A: The reason is because as moving person you liable to generate kilo volts of static that when touching a circuit can and will destroy parts or worst unseen damage. The strap insure that no static can built because you are grounded to cause this kind of damage. In the industry it is mandatory if NASA has a project in the works. Get caught without it you are fired......
What changes the voltage of a current?
First off, voltage and current are two completely different, yet related phenomenons.
Kirchoff's law states that Voltage = Current * Resistance (V=IR. So, to change the voltage in a given circuit while keeping current constant, simply change the resistance.
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As the voltage applied to a circuit increases the current and the also increase?
answer is actually voltage
It is simply the voltage of the system before the fault occurs.. Most probably this is the voltage of healthy system...
Why a dc shunt generator may fail to self excite?
If there is no residual magnetism in the field poles then there would be no flux too induce the initial voltage for self exitation
To increase the current you either need to reduce the resistance of the load or increase the voltage. Typically a higher wattage light bulb will decrease resistance or you could put multiple batteries in series.
What are the relationships between current power and resistance?
Power is inversely proportional to resistance.
Ohm's law: Current is voltage divided by resistance
Power law: Power is voltage times current, therefore power is voltage squared divided by resistance.
What is meant by short circuit in relation to vehicle electrics?
In electrical terms, a short circuit is an abnormally low resistance across the terminals of a power source, resulting in an abnormally high current-demand from the source, which typically exceeds its capabilities unless its output current is internally 'limited'.
How do you calculate voltage drop in a cable?
The answer to this question is simply ohms law. For most cables the resistance of the cable per meter will be defined by the manufacturer, so firstly multiply this by the length of the cable you are using.
Then apply ohms law V=IR. This will give you the voltage drop across the cable.
In most cases for domestic use, this value of R is so small the voltage drop is negligble, though using a cable with the lowest value R will give you the lowest voltage drop for any application.
If you're referring to a voltage drop in an Electrical Network the calculation becomes abit more complex and involves solving some implicit and explicit equations (assuming you know the voltage and power factor at the sending end and the real and complex powers consumed at the receiving end). If you wish to know more about this calculation let me know.
THIS CONSIDERATIONS SHOULD BE STRICKLY FOLLOWED: SOUND ENGINEERING AND ACCEPTABLE ECONOMICS;
1.DEFINE DEMAND LOAD - AFTER APPLYNG POWER FACTOR AND EFFECIENCY FOR MOTOR LOADS AND ACTUAL SYSTEM VOLTAGE AND PHASE.
2. ONE WAY LENGTH OF WIRE OR CABLE - FT. (AWG) OR MTR. (SQ.MM) SELECTION
3. MULTIPLY BY 125% TO THE CALCULATED LINE CURRENT TO GET AMPACITY REFERENCE
4. LOOK OR SELECT THAT NEAREST RESULT TO ANY LOCAL CABLE SUPPLIER CATALOGUE OR NEC TABLES AND MATCH IT TO CORRESPONDING CABLE SIZE.
5. APPLY DERATING FACTORS - ALSO AVAILABLE TO NEC OR CABLE SUPPLIERS AND DEFINE THE FF:
A. MEDIUM OF INSTALLATION - PVC OR RSC CONDUIT, CABLE TRAY OR CABLE LADDER OR TRUNKING, THROUGH, ETC.
B. AMBIENT TEMPERATURE - INDOOR OR OUTDOOR?
C. GROUP FACTOR - CONSIST OF CABLE SPACING AND DISTANCE TO WALL OR INSIDE CONDUIT INSTALLED IN TRAYS OR UNDERGROUND
6. APPLY DERATION IN WHICH RESULT IS LESS THAN ONE (1) TO THE PRE-SELECTED CABLE - THIS IS NOW YOUR ACTUAL FOR SELECTED CABLE
7. DEFINE REQUIRED OR ACCEPTED VOLTAGE DROP IN PERCENT VALUE
8. NOW USE THIS FORMULA:
VDapp(APPLICABLE VOLTAGE DROP) = %Voltage Drop x Actual Voltage x 1000 divided by Derated Current x One Way Length x 100
9. THE RESULT WILL HAVE A UNIT OF -- mV/A.Mtr OR MILLIVOLT PER AMPERE-METER
10. NOW COMPARE IT TO AVAILABLE TABLES FOR VOLTAGE DROPS OF CABLES - IF IT IS LOWER THEN SELECT THE NEXT SIZE OR WHICH EVER MEET THE REQUIREMENT.
you'll need to know the resistance of the conductor. copper has a certain amount of resistance per length. there are charts available on this
What changes occur to voltage-gated Na and K channels at the peak of depolarization?
Inactivation gates of voltage-gated Na+ channels close, while activation gates of voltage-gated K+ channels open.
What is the difference between mva and mw?
For clarification, the correct symbols are 'MV.A' and 'MW' -where a capital 'M' represents 'mega'. A lower case 'm' stands for 'milli' -quite a difference. And the symbols for ampere and volt are an upper case A and an uppercase V.
When an electric current flows through a load, the temperature of the load increases above ambient temperature, and energy is therefore lost to the surroundings through heat transfer. This represents a permanent loss of energy from the circuit. The rate at which this energy is lost is called the true power of the circuit, measured in watts.
At the same time, whenever current flows, a magnetic field is set up around the conductor. As the current increases in value during the first quarter-cycle, this field expands and energy is stored within that field. During the next quarter-cycle, as the current reduces in value, the energy stored in the magnetic field is returned to the circuit. So, while there is movement of energy, there is no net loss of energy from the circuit. The rate at which this energy transfer is taking place is called the reactive power of the circuit, measured in reactive volt amperes. (A similar thing happens in capacitive circuits, although the energy is stored/returned in an electric, rather than in a magnetic, field).
The vector sum of true power and reactive power is called the apparent power of the circuit, measured in volt amperes. That is:
(Apparent Power)2 = (True Power)2+ (Reactive Power)2
(Technically, there is absolutely no reason why true power, reactive power, and apparent power can't all be measured in watts -it is only traditional to use different units!)
It is very easy to measure the apparent power of a circuit, because it is the product of the voltage applied to the load and the current flowing through it -and we could use a voltmeter and an ammeter to determine these values. It is rather more difficult to measure the true power because the voltage and the current must be multiplied by the load's power factor, which is not necessarily known. Nevertheless, it can be measured directly, using a wattmeter.
What are examples of analog input devices?
Input computer devices are such as mouse,keyboard,joystick,gamepad,etc.They are basically used to provide commands to the computer so that they can work since it cannot work by itself without a command.
What is the purpose of a blocking capacitor?
At high frequency, capacitor can be considered as
1. Short Circuit in AC analysis.
2. Open Circuit in DC analysis.
{because Xc= 1/(2*f*pi) where f= supply frequency,pi=3.14}
As at high frequencies, in DC analysis, capacitor will be open circuited & can block the DC signal while AC signal is allowed to pass through.. Hence, this capacitor will act as a blocking capacitor for DC supply.
An electronic measuring device also known as a multimeter is used to check the electrical voltage in homes and industrial areas. The checks that need to be done before a multimeter is used is the to plug the black test lead into the black socket marked com. The red lead plugs into the red socket marked voltage and resistance.
Why does adding more resistance result in less current?
As the name implies, resistance resists current. In the mathematical formula, where E is electromotive force (voltage):- I = E/R If you increase the value of R (resistance), then the value of I (current) decreases.
Difference between dry cell and wet cell?
a dry cell is a cell that has electrolyte that is a paste
a wet cell is a cell that has a liquid electrolyte
-sads
What are the advantages of moving coil instrument?
Advantages are:- high sensitivity, uniform scale, very effective and reliable eddy current danping well shelded from any stray magnetic field. Disadvantages are:- very expensive, only suitable for direct current and voltages.
What is construction and working of single phase transformer?
The single phase transformer works on the principle of mutual induction.
Explanation:
When an alternating voltage V1 is applied to a primary winding, an an alternating current I1 flows in it producing an alternating flux in the core.
As per Faraday's law of electromagnetic induction, an emf e1 is induced in the primary winding.
Where N1 is the number of the turns in the primary winding's induced emf in the primary winding is nearly equal and opposite to the applied voltage V1
The first DC motor was made by a British scientist William Sturgeon in the year of 1832. The motor he made was the first motor capable of turning machinery.
What will happen if the resistance of the conductor increased?
According to ohms law, V = IR,
where V=voltage
I= current
R = resistance
the above formula can also be written as I = V/R,
here, resistance is inversely proportional to current. In other words,
as resistance increases, current decreases.
Can we verify ohm's law by using filament lamp?
The answer is NO.
Ohm's law states that current (I) flowing through the conductor is proportional to the potential difference (V) developed across its ends, keeping physical conditions such as pressure, temperature, strain constant.
In a filament lamp, the heating element used is Tungsten (W) which has high melting point and resistivity. Due to which , when current passes through it gets heated up and glows producing light and heat. As more and more, current flows through it, it gets considerably heated, resulting in increase of temperature. This is against the requisite condition "constant temperature". Hence Ohm's law cannot be verified using filament lamp because the temperature varies when the current flows through it.
What are the advantages of optical fiber over waveguide?
much wider bandwidth. Ie, many more signals can be run over the same cable.
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Optical transmission has several advantages over copper wire:
- optical fibre's high bandwidth means that a lot more data can be transmitted faster.
A pair of copper wires (which is what most houses in urban areas use for the initial point of access to the Internet can transmit two telephone calls simultaneously, while a single optical fibre can transmit over 80,000; - glass is cheaper and lighter than copper;
- optical fibre is unaffected by electro-magnetic interference, and so is ideal in electrically "noisy" environments, eg where there is high voltage equipment nearby;
- no electrical current is transmitted down a fibre (glass is a good insulator), so it is suitable in hazardous environments where electrical discharge would dangerous;
- as transmission technology continues to improve, higher and higher bandwidths are possible over the same optical fibre links without having to replace the cables.
