Electrical Engineering

Switching any two of the three phases will cause the motor to turn in the opposite direction. This rotation change should be done in the motor's junction box so that the colour phasing will remain accurate throughout the circuits system. For that reason, motors used where the direction of travel matters (like for elevators or escalators) are equipped with reverse phase relay devices that prevent the motor from operating unless the phases are wired in the correct order.

Switch two leads of the wires going to the motor for ex. L1,L2,L3 change to L1,L3,L2.

If this motor is wired for wye-delta starting, it will be easier to change the incoming power than at the motor junction box. Wye delta motors are six lead or twelve lead motors and lead pairing is critical on a wye delta setup. If the motor is started across the line like a standard nine lead motor, then by all means change it at the motor junction box.

speed of a dc motor can be varied by mainly two methods:-

1)field control method

2)armature control method

further ,

field control method can be divided in 3 parts:-

1)field rhestat control method---speed variation is acomplished by means of a variable resistance inserted in series with shunt field

2)reluctance control method---by changing the reluctance of magnetic circuit by choosing right material..

3) field voltage control method-requires variable field voltage supply.

and armature control method can be divided in 3 parts :-

1)armature resistance control---variable resisitance connected in series with armature

2)shunted armature control.

3)armature voltage control.

------------mrityunjay pandey

(kiit university ,btech 2nd year)

Not a good idea, without knowing more about the circuit in which it's installed.

Presumably, the 440v capacitor was selected because its max voltage rating (440v) is

higher than the instantaneous voltage to be expected at that point in the circuit. By that

criterion, the voltage at that point in the circuit may exceed 370 volts, and your proposed

replacement component won't hold it.

Because the series resonant circuit has the lowest possible impedance at resonance frequency, thus allowing the AC current to circulate through it. At resonance frequency, XC=XL and XL-XC = 0. Therefore, the only electrical characteristic left in the circuit to oppose current is the internal resistance of the two components. Hence, at resonance frequency, Z = R. Note: This effect is probably better seen with vectors. Clarification: Resonant circuits come in two flavors, series and parallel. Series resonant circuits do have an impedance equal to zero at the resonant frequency. This characteristic makes series resonant circuits especially well suited to be used as basic pass-band filters (acceptors). However, parallel circuits present their maximum impedance at the resonant frequency, which makes them ideal for tuning purposes.

we generate high voltage (DC,AC or Impuse) purposely for insulation testing of various components in power systems.

Physics labs need high voltage to accelerate subatomic particles.

OK, well Earth Loop Tester have a permanent magnet in it. When we rotate it, the flux cut the the conductor and consequently an emf is produced. As we connect the two point of the tester to the earth it complete the circuit and current start flowing through it.

The ratio of voltage and current give us the Impedance of Earth.

A GFCI outlet or breaker is designed to measure the current flow on both the hot and neutral wires connected to it. A "trip"will occur whenever the is a 5mA(millamp) difference between the two currents. Examples would be when you drop a hairdryer into water allowing power to flow through the water and not through the wires correctly. This system is designed as a life safety system to stop power from flowing through a person in case of an accident like the one I described.

Because Voltmeter measures potential difference BETWEEN two points so it should be connected to these two points and the only way for circuit and voltmeter to be both connected to the same 2 points is in parallel. Ampermeters measure the current THROUGH some circuit so the same current that is flowing through this circuit should flow through the ampermeter too. The only way is to let the current going through the circuit to go through the ampermeter later or before, so you have to connect ampermeter in series with your circuit. The fact that voltmeters have high resistance while ampermeters have low resistance is the side effect of the way how they are connected to reduce the error introduced by devices into measured value.

Adding more lamps in parallel (across) a line will cause total current to climb. It will keep climbing (increasing) until a load protection device (circuit breaker or fuse) breaks the circuit or until something fails because of excessive current.

This could be dangerous if you aren't very careful. Take the transformer out of the welding machine. Put it on a wooden bench. Apply 12 volts to the input side with a car battery. Measure the input volts with a volt meter and write down the value. Then use your volt meter to measure the output voltage. If you have no output voltage then your transformer is obviously blown. You should read an output voltage that is higher than the input voltage based on the number of winding in the coil and/or the manufacturers specifications. According to Faraday's law the only output voltage you will read is at the exact time power is applied to or taken away from the input when using dc power. Otherwise you will have to apply ac power which is much more powerful ( and more dangerous ) than the 12v dc. Your volt meter may not be designed to read high enough voltage for the output you would see with 110 v ac.

No. If the load is truly resistive, just measure the voltage across the load (in volts)and the current flowing in it (in amps) and multiply them. eg: 115 volts at 1.5 amps = 172.5 watts.

The significance is that Ohm's Law - together with the two Kirchhoff's Laws - are used all the time to do all sorts of calculations in circuits.

In theory, yes. In practice, no because the capacitors needed to do this would be several times the size of the house and much too expensive to purchase.

Use rechargeable batteries. Because they store energy in chemical form instead of just an electrostatic field they can store orders of magnitude more energy than capacitors can.

From Wikipedia's listing under the "war of currents" (http://en.wikipedia.org/wiki/War_of_Currents): In the alternating current system, a transformer was used between the (relatively) high voltage distribution system and the customer loads. Lamps and small motors could still be operated at some convenient low voltage. However, the transformer would allow power to be transmitted at much higher voltages, say, ten times that of the loads. For a given quantity of power transmitted, the wire size would be inversely proportional to the voltage used; or to put it another way, the allowable length of a circuit, given a wire size and allowable voltage drop, would increase approximately as the square of the distribution voltage. This had the practical significance that fewer, larger, generating plants could serve the load in a given area. Large loads, such as industrial motors or converters for electric railway power, could be served by the same distribution network that fed lighting, by using a transformer with a suitable secondary voltage. Bottom line: Less voltage drop across long distances of wire, and easily stepped up or down in voltage as needed. "One voltage fits all" approach.

A single phase induction motor has two sets of coils and a centrifugal start switch. The start winding is in series with the start switch. The start winding provides a rotating magnetic field in one direction enabling the motor to start. The motor can be reversed by reversing the connections of either the start winding or the run winding but not both.

in slip ring motors there are there are 6 power coil winding conductor and 3 terminal is starter winding first u1, v1, w1 give the supply l1, l2, l3 respitevly. Then star/del connectet on u2, v2, w2 terminal. Then anothe terminal k. L, m,are connect on veriable resustsnce then motor can be start.

Note: on high resistance is give on starting.

R = V / I (Ohms Law) A greater voltage results in more current. In the particular case of a light bulb, the resistance will change with current because its temperature changes. We assume here that the bulb is rated to take 200V.

When your computer contains loop, they can repeat the same set of code a lot.

The computer can repeat the code

hundreds, even thousands, of times.it is used for increament

*No

*that's not at all what the question is asking

*A "Mesh" is a small loop in a circuit. A "Loop" is a larger one, within containing several "Meshes".

*Most places use them interchangeably

AC or DC?? If it is DC voltages, series the sources together. eg. + 1.5V - to + 1.5V - = 3 VDC. If AC you will have to find a transformer in that range, 1.5VAC primary to 3VAC secondary.

For a specific voltage, current flow is inversely proportional to resistance.