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Induction Stove
As all we know,induction stove works on the principle of electromagnetic induction.Thus an emf is induced in the vessel and eddy current flows through the vessel.Since the vessel is made of ferromagnetic material (high resistivity) larger amount of heat (H=I^2 R)is generated.What will happen if a human body comes into contact with this high resistive vessel??? Won't the human body resistance be parallel...
SGhosh
- May 15th, 2012
Human body under dry condition has much higher resistivity compared ferromagnetic material.
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Why is r.m.s. value used to express a.c. quantities?
SURAJTHEGREAT
- Apr 10th, 2011
AC values are always alternating.Hence we cannot make a precise analysis!!!!So we use RMS value.Let us consider a bulb B.IF it is switched to position A(it is connected to ac supply).IF switched to po...
raviiisc
- Apr 9th, 2011
The rms value arised in the following manner:The heat dissipation with AC supply will found, then the DC supply is applied such that same heat production in resistor. That DC voltage value is said to ...
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Heater Effect on Bulb
If Heater of 1000W is connected in series with 60 W bulb. what is the effect on the bulb.
SURAJTHEGREAT
- May 5th, 2012
1 Thing everybody has to remember is that only current and not the voltage remains constant across the elements.Let us assume that the elements in series are connected to 220V supply source. Total po...
bittu123
- Nov 9th, 2011
@ om_zzz
You are right, bulb will glow but dimmer and heater will not heat-up(more precisely it will generate very less heat) -
Transformer Signal
What is the benefit of using ac signal in a transformer?
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sinhasunilk- Member Since Jul-2010 | Jul 3rd, 2010
Transformer can only operate with A.C supply. Voltage will induce in the secondary winding of transformer only when there is a change in flux. The induced voltage in the secondary winding is no. of turns in secondary x rate of change of flux. In D.C circuit the rate opf change of flux is Zero, hence induced voltage in secondary winding is Zero and no Back MMF produce in the magnetic circuit of core of transformer. This will result in very high current drawal in the primary winding and will result in burning of primary winding of transformer. We can not think of applying D.C source in transformer.
SURAJTHEGREAT
- May 5th, 2012
The reason why dc signal cannot applied to a transformer is that f=0,reluctance is 0,very high current flows through windings and it is burnt out!
sinhasunilk
- Jul 3rd, 2010
Transformer can only operate with A.C supply. Voltage will induce in the secondary winding of transformer only when there is a change in flux. The induced voltage in the secondary winding is no. of tu...
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Variable and Core Losses
Why copper is called variable loss & core loss is constant loss?
SURAJTHEGREAT
- Feb 22nd, 2010
Iron loss-When an electric current flows through a copper conductor (or any conductor), some energy is converted to heat. i(square)*r...this equation is obvious that iron loss depends on flowing curre...
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Phase Sequence
What happens when we change the phase sequence in 3 phase system?
R Raghavendran
- Feb 26th, 2010
Only the sequence of rotation of Magnetic fields changes, which causes a change in the rotor rotating direction accordingly.
SURAJTHEGREAT
- Feb 22nd, 2010
There is no change for ordinary devices,(behaves same as if the unvaried 3 phase supply is given) The rotation direction of the machines varies with variation in sequence of ac supply..
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Voltage Source
What would happen if two voltage sources of different magnitude are connect in parallel?
anilsabaji
- Jan 8th, 2010
If the two sources, say batteries with voltages V1 and V2, and internal resistance R1 & R2 are connected in Parallel, then a current equal to to (V1~V2)/(R1+R2) will circulate between them assumin...
nagarjuna227
- Dec 20th, 2009
We cannot find the voltage across two different magnitude voltage sorces.
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Power Factor
Why the Voltage rises when Leading Power Factor is occurs?
shobhit bansal
- Apr 3rd, 2009
When there is a case of leading power factor, that means synchronous generator works in over excitation mode, reactive power will be generated, and as we know that change in voltage is directly prop...
SURAJTHEGREAT
- Mar 18th, 2009
We know flux is 90 degree ahead of voltage...If leading p.f. load is connected,the armature flux and main flux aid each other,Bcoz current(field current=flux)is 90 degree ahead of voltage. (Thus 2 fluxes aid each other)and since voltage propotional to flux,voltage increases..
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Purpose of Earthing
What purpose does an earth serve on a generator terminals if the generator was started accidentally.This a true incident when the generator was started it blew the earth wire because the terminals were shorted and then earthed to ground. What is the point of earthing if it cannot save the generator or the personnel.
nrathi.thb
- Dec 23rd, 2009
The earthing wire was not of proper size to bear the fault current & may be also the earthing was not done as per specification.
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Three Phase Induction Motors
Why capacitors are not used in 3 phase induction motors?
mohann2008
- Apr 11th, 2009
In three phase induction motors, capacitors are not needed, because when the current passes through three wires, three magnetic fields will be produced. Due to the interaction between those magnetic fields, RMF will be produced automatically without the help of capacitors.
naresh20047038
- Mar 20th, 2009
In 3 phase Induction motors rotating magnetic field will be created which in turn interacts with the rotor conductors resulting in rotation of rotor, so there is no need of capacitors for starting pur...
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Units Calculation
How many units will a 40W tube consume in 1hr 15 minutes 20 seconds?
SURAJTHEGREAT
- Mar 2nd, 2009
1 unit=1000 watts.Therefore 40 watts=0.04 units.(40/1000)If the light consumes 0.04 units for 1 hour.then for 15 min it is (0.04/4)=0.01 unitsI calculated this way(1 hr=4*15 min...Then for 15 min(divi...
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Induction Motor
Why transformer does not rotate like induction motor. Inspite both having same principle?
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Magnets in Speaker
Why magnets are used in audio speaker?
SURAJTHEGREAT
- Mar 3rd, 2009
We know audio signals are going be as signals (ac signals are those whose amplitudes are constantly changing). The speaker system employs 2 magnets. 1-Electromagnet, 2-Permanant Magnet. When 2 mag...
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Vector Quantity
Is current a Vector quantity? If yes, then two wires on 90 degree angle must have resulting current equal to zero.
SURAJTHEGREAT
- Mar 3rd, 2009
According to me, current is neither scalar nor vector completely. It does not obey, vector law of addition. We know kirchoff's law, Current leaving = current entering. So if load is connected at the...
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Neutral Point
Why neutral point is not required in high transmission line?
Karuppiah arumugam
- Apr 27th, 2015
Power system having Generation,transmission and distribution . Distribution transformer only need neutral becoz we need lighting load supply. 230V (phase to neutral 230v) in the transmission system only we sending voltage from one end to another end
SURAJTHEGREAT
- May 5th, 2012
HVDC Transmission lines are carriers of power,they are not source of generation.if there is any fault in HVDC,the extra current has to flow through generator,transformers...since alternators and trans...
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Reactive Power
What is mean by reactive power? How it is generated?
Sreebai
- Sep 21st, 2010
Reactive power is the power required to transmit the active power. The reactive power is like an envelop,that is used to send a letter. Without this we cant send the active power and it cant be too hi...
SURAJTHEGREAT
- Mar 3rd, 2009
We know reactance (hypothetical resistance) which reduce the supply voltage by opposite flowing induced emf. This power loss due to reactance is known as reactive power. This power is not useful power. It is a waste. However it is useful in determining the phase angle.
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Neutral Earthing
What is neutral earthing and equipment earthing?What are the advantages of grounding a neutral of a transformer and gernator?
SURAJTHEGREAT
- Mar 3rd, 2009
Nuetral point is useful. Bcoz the extra current flows to the ground. Ground is always at a higher polarity than the device. For example consider your instant heater. It always is a 3 pin plug point....
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PID control
Give brief detail on PID Control.
SURAJTHEGREAT
- Mar 3rd, 2009
A controller is a device employed to obtain a stable output. There are many controllers of that PID controller is the most widely used. A proportional–integral–derivative controller (PID...
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Wattmeter reading
Why does wattmeter's reading go negative?
bittu123
- Nov 9th, 2011
Suppose, phase difference between V and I is "A"(angle). and wattmeter reads +ve. Now if phase difference became (A+180), wattmeter will read -ve of same magnitude.
It simply means, direction of power flow gets changed just because of changing in direction of either current or voltageSURAJTHEGREAT
- Mar 3rd, 2009
If you have seen the wattmeter ratings, it will be (300V,10A,UPF) (Voltage, Current, Power Factor) That is wattmeter needs voltage and current to measure power. So a wattmeter consists of t...
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Exact Time
A clock was set right at 5 am then it loses 16 minutes every day, on the 4th day when it shows 10 am, what is the exact time.
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prasannamohandas- Member Since Oct-2009 | Oct 28th, 2009
3 days 48 min.... lost
4th day for 5 hrs.....5/24*16 min =3.33 min.... so total 51.33 min...
exact time will be 10:51.33 hrsSarvinder Kumar
- Jul 6th, 2016
11.04
karthik
- Jun 25th, 2016
11:04
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Electrical Ceiling Fan Rotation
Why ceiling fan rotates in anticlockwise direction?
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balls
A sporting goods store ordered an equal number of white and yellow balls.The tennis ball company delivered 45 extra white balls,making the ratio of white balls to yellow balls 1/5 :1/6how many white balls did the store originally order for?a)450 b)270 c)225 d)none of these
anilkumar_cse
- Apr 1st, 2010
Given ratio is of white and yellow balls and it is 1/5:1/6.=> 6:5=> Therefore the total balls are in 11 parts.=> so the total balls delivered must be divided by 11.=> From the answers 450 + 45 is divided by 11, so the answer is a=>450
milindnsec
- Dec 30th, 2009
Let there is x no of each ball, when 45 white ball is added total number of white ball = x+45 now accordingly x+45x=...
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Power Factor
What do you mean power factor?What is the use of Power Factor?
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rahulr30- Member Since May-2008 | May 30th, 2008
Power factor is the ratio of Active ppwer to apparent power in sysytem,It is an index to see how much of the energy is actually being utilized to do useful work
veerateja
- Jun 11th, 2011
pf is the co-sine of phase angle b/w voltage and current.Generalley it is leading or lagging depanding on the load whether it is inductive(lag) or capactive(lead).Take voltage as reference the current...
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To find the day of the week
Find out what day of the week was January 12, 1979?
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bharat bhushan- Member Since Feb-2008 | Feb 13th, 2008
when we move down in yearwise a day decreases. but when a leap year comes 2 days gets decreased..for e.g.
12 jan 2008 --- saturday
12 jan 2007 --- friday
12 jan 2006 --- thursday
12 jan 2005 --- wednesday
12 jan 2004 --- monday..
so in 4 years five days gets reduced... so in this manner we can find out in which year wat day was on 12 jan..
ANSWER ----- it was friday on 12 jan 1979......SURAJTHEGREAT
- May 29th, 2010
jan 12,1979- lets determine the no. of odd days upto year 1978-(1600+300+78)1600 is divisible by 400,therefore the no.of odd days is 0...300 yrs has 1 odd day78yrs consist of (19 leap + 59 ordi...
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Why we are using Sinusidol wave in all electrical systems?
SURAJTHEGREAT
- Apr 19th, 2011
We know flux(phi)=NBA cos(teta)e=-d(phi)/dttherefore on differentiating we gete=NBAw sinwt.ie.sinusoidal wave.Moreover when 3 phase are displaced by angle 120 with respect to each other,rotating magnetic field is produced.
cvk
- Oct 6th, 2007
Reson 1 is the way power is generated. Due to the construction of generators, the default wave form is sinusoidal. Secondly, the frequency of sine wave is a single definite value while other wave form...
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Electrical Engineer Interview
1. what is the different between CGS system and MKS system? 2. When we connect the capacitor Banks in Series with the circuit 3. What is the difference between Earthing & grounding 4. how much voltage is present in neutral resistance?and how much voltage is present in earth resistance... 5. What is the purpose of calculating knee point voltage for Current transformers? 6. What is the voltage drop for...
SURAJTHEGREAT
- Apr 10th, 2011
When capacitor is connected in series with the supply source (dc battery) ,capacitor gets fully charged and as a no current flows to the load!!!! When capacitor is connected in series with the supply source (ac) ,a leading current flows through the load.
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what time is it now? the no. of minutes from midnight to now is 9 timesthe no. of minutes from now to nooN
Akhilesh
- Apr 5th, 2021
10:5
SURAJTHEGREAT
- Mar 9th, 2009
12*60=720 min....Let x be the no.of minutes it is behind noon....therefore 9x=720-x minutes...10x=720x=72....72 minutes behind noon 12 is 10:48 am...Now the time is 10:48 am,72*9=648 min....648min+12(a.m)=10:48 a.m.(600/60=10hrs +48 min)thus verified....
