0
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 resistance of the circuit if current flow is 6 amperes in a 120-V circuit?
Google Ohms Law. It will give you all the formulas you need to compute Ohms,Volts and Amps. Simple formulas :-)
Why a DC motor starter is called 3 point starter?
Because it has three terminals L , F and A
L - Line (connected to Supply)
F - Field (connected to field of dc motor)
A - Armature (connected to armature of DC motor)
that's y it is called 3 point starter :)
yes
By definition, the terms 'leading' and 'lagging' refer to what the load current is doing with respect to the supply voltage. So, for a 'lagging power factor', it is the current that is lagging.
Why you use the star delta connection?
Advantage:
Star Connection:
- In a star connection, phase voltage Vph = VL/ (3)1/2. Since the induced emf in the primary winding of an alternator is directly proportional to the number of turns, a star connected alternator will require less number of turns than a delta connected alternator for the same voltage.
- For the same line voltage, a star connected alternator requires less insulation than a delta connected alternator. Due to the above reasons three phase alternators are generally star connected.
- In star connection, we get 3-phase and 4-wire system. This permits the use of two voltages (phase voltages as well as line voltages). Single phase loads can be connected between any one lie and neutral wire while the 3-phase loads can be put across the three lines. Such a flexibility is not available in delta connection
- In star connection, the neutral point can be earthed. Such a measure offers many advantages. For example, in case of line to earth fault (L-G fault), the insulators have to bear 1/31/2 (57.7%) times the line voltage. Earthing of neutral also permits the use of protective devices (relays) to protect the system in the case of ground faults
Does plastic protect you from electric current?
No, practically all plastic is an insulator. An insulator does not carry any electrical currents. A conductor can carry a current.
"What plastics are conductive?", you may ask -- see link below.
Every component in a series circuit must have a potential difference across its terminals if current is to flow through that component. We call each of these individual potential differences a 'voltage drop', which is actually a bit of a misnomer as it's not really a 'drop' at all; it would be better termed a 'distribution'. The sum of these 'voltage drops' will then equal the supply voltage applied to the entire circuit.
Why transformers rated in MVA not in MW?
Transformers are rated in KVA and MVA. The load determines the power factor. It is obvious to multiply the VA with cosine angle to get Watts or Kilo watts. While manufacturing the transformer or at its installation we don't know the load power factor. Hence we could not determine the rating in Watts or kilo watts or Mega watts. We simply note it as VA or KVA.
S.Dhanabal
A current is measured in which unit?
The Ampere, also in shortened form 'Amp' or "A". It commonly uses the symbol "I" in calculations, hence Ohm's law is in the form V = I x R
What is the fundamental frequency?
For a waveform containing harmonics, the harmonic frequencies are multiples of what is known as the 'fundamental' frequency. For example, for a waveform that contains 'third harmonics', the fundamental frequency is one-third the frequency of the harmonics.
The fundamental frequency of vocal folds the speech mechanism as sound generator.
What are the three basic parts of transformer?
- core - air, iron, ferrite, etc.
- windings - one or more coils wound around the core.
- bobbin - insulating structure used to hold the windings. optional, not needed in every type of transformer. in some types of transformer the windings are prewound on the bobbin then the core is inserted into the bobbin.
How many volts are in lighting?
If you want to run a typical 3.4 volt LED from a 6 volt supply at its maximum rated current of 30 ma, then divide 2.6 by .03. This indicates 87 ohms. The next higher popular standard resistor value is 100 ohms. Please beware that I consider the 30 ma rating for 3.4-3.5 volt LEDs to be optimistic.
How do you design the transformer?
You can construct a transformer, and it's not particularly difficult if you know what you are doing. It's not possible to give you detailed instructions without knowing what type of transformer you need, and the answer to that depends on what it's for. A transformer consists of two coils of wire, electrically insulated from each other but magnetically coupled. How the coupling is done depends mostly on the frequency of operation. For electric power ( 50 or 60 Hz ) the coupling must be very tight, so the coils are wound onto an iron core. For audio frequencies you would generally do the same, although a ferrite core is a possibility. For radio frequencies, the transformer would be wound on a ferrite core if you need tight coupling for power transfer. Otherwise it might be wound without a core (usually referred to as an air-cored transformer). Please repost the question, saying what the transformer is intended to do.
What are the advantages of a silicon-controlled rectifier?
SILICON CONTROLLED RECTIFIER APPLICATIONS i) Speed control for motors ii) Temperature control for electric hot plate iii) Dimmer switch for domestic lighting iv) Dimmer control for stage lighting.
Are the contacts in a potential starting relay normally open?
The contacts are NC Normally Closed and open when the back emf is high enough to pull the contacts open and take the start capacitor out of the circuit.. usually at about 75% speed of motor.
What is the significance of Synchronizing Power Coefficient?
The measurement of stiffness of the electromagnetic coupling between the rotor and the stator is carried out by the synchronizing power coefficient. If the value of Psyn is large, the coupling is stiff or rigid. For a too rigid coupling, with change of load or supply, the machine will be under shock which may damage the rotor of the winding
Why pole shoes are laminated in a dc machine?
they are used to protect windings to get down and spread the flux uniformly.
Define the electrical term VA?
'VA', or more correctly, V.A, is not an electrical 'term'. Rather, it is the symbol for 'volt ampere', the unit of measurement for a quantity called 'apparent power'. This is the product of the supply-voltage and load current for an a.c. load.
What will be the output when a square wave is the input of the differentiater?
If you use a square wave as input to an integrator circuit, the output will be a triangle wave.
What is the advantages and disadvantages of single phase and three phase?
Single phase inherently requires less equipment (it's cheaper). Three phase motors are more efficient than single phase.
What is the symbol of a diode?
The letter used is called a Reference Designation, and for a diode sometimes depends on what kind of diode it is. Most diodes use the letter D, as in D1, D2, D3. Zener diodes usually use the letter Z or much more rarely ZR or ZD (Zener Rectifier or Zener Diode). CR is an archaic designation that stands for Crystal Rectifier.
LEDs may use LED1, LED2, etc. or just D1, D2, etc.
A bridge rectifier (four diodes connected so AC fed into two leads results in pulsating DC from two other leads) uses BR for obvious reasons.
AE7HD
The letter symbol for the diode is D.
Why Oled has low power consumption than led?
because oleds are light emitting themselves therefore they need no background illumination which uses much power (CFL more than LED Backlights)
What is the purpose of the automatic voltage regulator?
The purpose of an adjustable voltage regulator is to have a regulator that can give out variable voltages. This is in contrast to a fixed voltage regulator which only outputs one voltage, which it is rated for.
To allow for adjustable voltage, usually the resistors on the output of the regulator just need to be swapped for different values to give differing output voltages.
Inverse Definite Minimum Time Lag = IDMT relay
It's a electromagnetic type rotating disk relay.
Tripping time of relay decreases with increasing fault current.
see http://myweb.tiscali.co.uk/robert.booth/uni/docs/Power%20Supply%20Assignment%203.pdf
