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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
Is internal resistance of a cell a defect or not?
no internal resistance of a cell cannot be considered to b as a defect because the resistance is so small as compared to the output we get from a cell this ristance can be neglected..
What generator size is needed for 40 hp 480 volt 3 phase motor?
probably about 50 hp
depending on how reliable the efficiency ratings of the various manufacturers are
Not all 'short circuits' are 'dead-shorts' -i.e. the resistance between the two conductors (or a conductor and earth) is not necessarily zero ohms -especially when the insulation between them has not completely broken down. The actual resistance is called the 'fault resistance'.
Why is the voltage decreased again before electricity is supplied to homes?
It needs to go to all the homes and increases current i dont know if thats right its just a guess.
Is the current pass through parallel short resistance?
no.because current always try to flow trough low resistance path.as short circuit has low resistance current pass trough short circuit
How capacitor used in a timing circuit?
A capacitor relies on the time it takes for the voltage across it to reach a certain value. When it is fully discharged, it acts like a piece of copper wire. ie: it conducts. The voltage across it now is zero. When a voltage is applied to it, it begins to charge, and so the voltage measured across it's terminals increases. This takes time. How much time depends on the voltage applied resistor connected to it and the value of the capacitor.This voltage is then used to energies a relay, turn a transistor on, fire an SCR, and lots of other things.
When you short out a resistor in a parallel circuit why does the current lower?
The total resistance of a set of resistors in parallel is found by adding up the reciprocals of the resistance values, and then taking the reciprocal of the total. By removing a resistor the total current will lower. If you short out the parallel circuit as suggested it will take out the fuse that should be protecting the circuit.
AnswerShorting-out a resistor in a parallel circuit, will act to short out the entire circuit, therefore, significantly increasing, not lowering, the current! And, as the previous answer indicates, this short-circuit current will operate any protective devices, such as a fuse.
In a parallel circuit current does not lower but it will be increase if shorting-out one resistor in the two resistor parallel circuit, the circuit will become very low resistive and the larger current will flow through the short path.
Why rotating magnetic field is not produced in a transformer?
Even an emf is induced in the rotor also, with similar synchronous speed, but owing to large inertia of rotor, it cannot attain synchronous speed and stays standstill.
In case of transformer, the three-phase windings are wound on three limbs - on each limb LV winding is wound on the core and then HV winding is wound over the LV winding (for increased efficiency of transformer). Due to this constructional arrangement, a rotating magnetic field is not visualized in transformer, rather mutual inductance comes in to picture.
24VACRMS * 1.414 = 33.94VACPEAK
The unloaded filtered DC voltage is 33.94V
The unloaded unfiltered voltage will be a single polllarity AC voltage with a peak of 33.94V
What is the condition of maximium power transfer of circuit?
Maximum power transfer happens in a circuit when the resistance of the circuit equals the reactance.
Impedance Z = R + jX. At R=X, maximum power transfer happens.
For many years, mainland Western Europe has used a mains electricity supply rated at nominally 220VAC @ 50Hz, while the UK used 240VAC @ 50Hz. Currently, ALL Western European supplies are classified 230VAC and most other countries follow this. However the US and Canada use 120 V @ 60 Hz.
A stator is the stationary part of an electric motor. The stator contains the windings in which the electrical source is connected to. The rotar is the core and shaft that rotates when electricity is applied to the stator
How speed of a squirrel cage induction motor can be varied?
There are two ways of changing the speed of AC motors,by altering the frequency or the number of poles in the motor. An increase in frequency of the supply voltage to the motor will cause it's speed to increase while reducing the frequency will causes the motor speed to drop. This is the method exploited by Variable Speed/Frequency Drive. The second method of changing the number of motor's stator poles is the difficult. The manufacture must design the motor such that the number of the motor's pole in operation can be increased or reduced. Increasing the number of poles increases the stator flux density which decreases the speed. Decreasing the number of poles does the opposite. This method is typically found in two speed motors and it's rarely used compared to VSDs.
How starting torque of an induction motor can be increased?
For a single phase motor, this can be done by connecting a capacitor in series with the starting windings. For three phase motors, this can be done by connecting starting resistors in the stator windings at starting. This reduces the stator current and hence it's flux density. Thus the rotor will have less opposition starting to rotate. Hence, the torque has increased.
Where should ac or DC supply be used?
The type of power supply being used (AC or DC) should match the power requirements of the device it will be supplying power to.
What is the resistance of a clothes iron that draws a current of 12A at 120V?
By Ohm's Law Voltage = Current x Resistance
R = V / I = 120 / 12 = 10 Ohms
Leading angle means that the current lead voltage by 90 degree,which implies a capacitve load. while,lagging angle mean when the current lag the voltage by 90 degree or when the voltage lead the current by 90 degree.which implies an inductive load.
What size generator do you need to move a 30 hp electric motor?
A 5 kW generator would turn it over but if the full 30 hp of mechanical power is needed, that would require about 30 kW of electric power from the generator.
pcc is the power control center, in which all distribution switches are installed and operated here
What is loading affect of multimeter?
'Loading effect' applies to voltmeters, or to multimeters when set to measure voltage. It describes the change in a circuit's resistance when the resistance of the voltmeter is taken into account. It's effect is to cause the resulting measuredvoltage to be different from the actual voltage which would appear without the voltmeter connected. The loading effect is minimised by ensuring that the internal resistance of the voltmeter is significantly higher than the resistance of that part of the circuit to which it is connected. For general voltage measurement, this is usually the case anyway, but when measuring circuits which, themselves, have very high resistance care must be taken over the choice of voltmeter to be used.
