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
Why are iron losses constant at all loads in a transformer?
because iron loss is depends on frequency and it is constant through out the operation ...irrespective from load
Why does vcc voltage called vcc?
I believe that Vcc stands for Voltage Common Collector. This is because the voltage is hooked up to the collector of the transistor.
What are the implications for relevant parties when carrying out the safe isolation procedure?
Electric shock , burns ..
Before you start work, you need to ask yourself " are you a competent person and do you follow the correct procedures for correct isolations of supply? " You must follow safe isolation procedure and should supply all the relevant training, safety equipment, PPE and signage.
1. State the implications of NOT carrying out safe isolation procedures to the following...
a) Yourself
- put yourself and others around you at risk ..COVERED IN NEXT PART
- liable for prosecution
b) other personnel
- can accidentally put them selfs and other people in the area at risk
c) customers/clients
POSSIBILITY OF PROSECUTION IF ANYTHING GOES WRONG, POTENTIAL LOSS OF PRODUCTION / INCOME GOODWILL.
d) public
- can accidentally put themselfs and others at risk without knowing
e) building services
POTENTIALLY CAUSE DAMAGE TO OTHER PARTS OF THE INSTALLATION
2. State one implication of safe isolation procedures to the following
a) other personnel working within the building
- could be without power whilst isolated
b) customer/clients
COULD LOOSE ACCESS TO PART OR ALL OF BUILDING AND OR EQUIPMENT
c) Members of the public
COULD LOOSE ACCESS TO PART OR ALL OF BUILDING
d) Building services which require electrical supply
COULD LOOSE USE OF LIFTS, ESCALATORS, HEATING, COOLING AND DRAINAGE.
- could be without tools and equipment which may stop work while the isolation is in place
What do you mean by resultant current?
The sharing of current between different components in an AC circuit
What are the Advantages of bundle conductors over solid conductor?
By bundle conductors, I am assuming that you mean stranded conductors. If you actually mean bundles of wires, then the bundles could be either stranded or solid and your question does not make sense.
Stranded conductors have two main advantages over solid conductors. The first is flexibility. Stranded conductors are much more flexible than their solid counterparts.
The second main advantage is skin surface area. Alternating current tends to travel towards the outer skin of a conductor. This is known as the skin affect. Stranded wire has a lot more skin surface area than solid wire does.
There may be more advantages, but these are the two I could think of off the top of my head.
What is difference between interposing voltage transformer and potential transformer?
potential transformer is to maser and protection purpose the ivt is used for synchronicing purpose
In the fixed.bias biasing several key parameters of the amplifier depend on the Beta of the transistor. This parameter has a wide variation (often 5 to 1 or more) for a particular transistor type. Thus, if you need to make a production run of a number of identical amplifiers, this variation in the Beta is unacceptable.
In the voltage-divider stabilized method the performance of the amplifier is independent of Beta (or almost). Thus, this design is suitable to be used in the production of a large number of identical devices.
In terms of biasing, a voltage divider circuit helps offset the effect of changes in the beta value of the transistor. So it's said to be more 'stable' because heating of the transistor, or swapping transistors entirely (both of which affect beta) will not greatly affect the output of the circuit.
As far as the actual output is concerned, I believe both circuits have similar input/output impedance ranges and similar voltage gains. But the fixed biased circuit typically has more current gain.
What is direct online motor starter?
As the name recommends, Direct-On-Line beginning implies that the Motor is started by
associating it straightforwardly to the supply at appraised voltage. DOL Motor Starter is reasonable for stable supplies and mechanically firm and very much dimensioned
shaft frameworks.
What is difference between 0.8 leading and 0.8 lagging power factors?
Power factor measures the phase difference between voltage and current. If they are in phase the Power Factor is one. If the current and voltage are out of phase the power factor is between zero and one. You can describe the PF by saying the current lags the voltage with a PF = .8 or the voltage leads the current with a .8 PF.
Why you use 2core cable for Dc motorCan you use 3core?
Mostly for small dc motor, 2core are used. earthing can be achieved by grounding the chassis.
How can you get negative voltage?
Your question should read "How do you get a negative potential?", for the reasons explained below.
The term, 'voltage', is another word for 'potential difference'. The terms 'positive' and 'negative', when applied to a potential difference or voltage indicates the sense (or direction) in which the potential difference or voltage is acting. For example, if a second voltage is acting in the same direction as another voltage then it is acting in the positive sense; if it is acting in the opposite direction then in is acting in the negative sense'.
It's very important to understand that you cannot apply 'positive' and 'negative' is the sense of charge or polarity to potential difference or voltage. You can, however, apply these terms to 'potential'. Potential is relative, and always measured with respect to a given point (often, the earth). So a point can be, for example, +5 V or -5 V with respect to another point (usually earth or ground, but not necessarily).
Never confuse 'potential' with 'potential difference' and remember that 'voltage' means potential difference notpotential.
So, to obtain a negative potential, earth (ground) the positive terminal of the battery or d.c. supply. All potentials measured relative to earth are now negative. To obtain a positive potential, earth the negative terminal of the battery or d.c. supply instead. All potentials measured relative to earth are now positive.
If you want to get a negative potential,
- Earth the positive terminal of the DC power source
- Connect a resistor in series with the negative terminal of the source
- At the other end of the resistor you get a negative potential (the value's less than the value of the power supply)
What is dc regulated power supply?
A: DC can be unregulated and operate circuitry however that becomes impractical when the source varies continuously or wildly A regulator simply will provide a lesser power requirement but at a reliable level not matter of the source swing.
How do you interpret circuit diagrams and other relevant specifications?
you interpret circuit diagrams by following the copy's you have been given too work from, understanding the symbols r show in different format from the actually connection!
What is synchronous reference frame?
It has been shown that the speed of rotation of the d.q axes can be arbitrary although there are three preferred speeds or reference frames as follows:
(a) the stationary reference frame when the d,q axes do not rotate;
(b) the synchronously rotating reference frame when the d,q axes rotate at synchronous speed;
(c) the rotor reference frame when the d,q axes rotate at rotor speed.
How do you convert to watts to horsepower?
To convert Watts (W) to a horsepower rating (HP) simply multiply the Watts by 0.00134
W x 0.00134 = HP
How do you increase the inductance in a inductor?
Since we know that inductance of an inductor depends on the length of inductor by the formula
L=muAN*N/l, where l is the length of inductor. So by varying the length of inductor we say that inductance of inductor varies.
How can you say that ac emf is induced in the coil?
When we place a current carrying conductor in a magnetic field emf is induced in a coil. we can knoe it by connecting voltmeter.
Why low power factor need surcharge?
Low power factor leads to higher current in the system for the same real power requirement. (Check out the power triangle in any basic electical engg. book)
higher current leads to higher system losses for the supply & distribution companies, drop in voltage, also necessiates higher sizing of system components.
Hence low power factor attracts penalty also on the other hand some distribution companies provides incentives for maintaining higher pf.
Regards,
Sameer Shaikh
What is vector impedance meter explain with circuit diagram?
A vector impedance meter is used to measure impedance and phase angle, this is done by calculating voltage and current through an impedance and then calculating Z and phase angle with that, now there are two modes for operation i.e constant current mode and constant voltage mode.
CONSTANT CURRENT MODE
construction = first of all there is a wien bridge oscillator(w) to choose frequency then an AGC amplifier(a) to regulate current then a z switch control(zs) which regulates gain of AGC amplifer,
feedback to AGC amplifier is done by an dc differential amplifier(dc)
dc
|
|
|
w--------->a--------->z
now there is an ac differential amplifier too(ac) which gets one input from the z switch and one from the unknown impedance(imp), and there is a transconductance amplifier too which gets one of his input from the unknown impedance
dc<-------------------------------------------
| |
| |
| |
w--------->a--------->z----------->ac-------------|------------> z meter
| | |
| | |
_____| | |
| | |
| | |
| | |
imp | |
| | |
|________|___>rt___>|
working---> in constant current mode we have to maintain constant current through impedance so current is made to come to unknown impedance from z switch, then that current goes through trans-resistance amplifier, which converts that current to a voltage that is sent to a dc differential amplifier and is compared with a reference voltage in dc differential amplifier then the difference between voltages is amplified and sent to AGC amplifier, so AGC together with z switch this way maintains constant current through unknown impedance,
now for calculation z-magnitude,
ac differential amplifier gets input from unknown impedance and z switch, so difference is amplified and sent to a band pass filter which filters out then the filtered signal is sent to a z-magnitude meter which is calibrated to read z directly.
What will happen when a dielectric slab is inserted in the parallel plate capacitor?
(a) Charge Will increase
(b) Potential difference will stay the same
(c) Capacitance will increase
(d) Stored energy will decrease
Does the motor speed double when the armature voltage is doubled?
Yes, because as the armature voltage increases, the speed also increases so they are proportional.
How could you calculate the resistance of a circuit?
A variety of techniques can be used. Node-Voltage and Mesh-current (or Loop-current) methods, for example. See related link for examples. If there is a single voltage source in the model, then find the current supplied, and Resistance = Voltage/Current. {R = V/I}
You could simulate/ model the circuit on a computer then apply the power profile and a current value will be calculated. Or if you have the circuit working, Place an amp meter into the circuit and measure the current. V/i = resistance.
