Electrical Engineering

watt meter is constructed such that it read only power on a single scale. Only single scale will available to read the measured power. In order to take the accurate reading just we measure the reading and we will multiple along with factor called multiplication factor. That's depends on on which voltage knob we connected and also the current. Multiplication factor can be determined by: Multiplication factor =(voltage range*current range*pf)/Max scale deflection.

An ammeter is an instrument designed to measure electric current, which is expressed in amperes. A d.c. ammeter is one that will measure direct current (d.c.), as opposed to alternating current (a.c.).

Ammeters are rarely used outside laboratories. Instead, multimeters are more commonly-used, and these will measure d.c. or a.c current and voltage, together with resistance. In other words, a multimeter functions as an ammeter, a voltmeter, and an ohmmeter.

The principle of operation of a digital ammeter is too complicated to explain in this forum. An analogue ammeter works by a rotating coil to which is attached a pointer. The coil is balanced between two hairsprings and located between opposite faces of a permanent magnet. When current passes through the coil, the resulting magnetic field reacts with the permanent magnetic field, causing the coil to rotate, tightening the hairsprings. When the torque due to the current matches the opposing torque due to the hairsprings, the coil will stop turning. The position of the pointer on a scale will then indicate the current passing through the ammeter.

no the strength of the magnetic field does not decrease because of the number of coils increases.

It does have armature resistance.

You can make a voltage divider set of resistors and tap off the desired voltage. Some voltage regulators can be fed much higher voltages. The regulator will provide a constant settable voltage with short circuit and overload protection. There are DC to DC converters. They first turn the DC into AC then rectify it and produce DC.

V=IR

you are adding in parallel, so V is non-zero, because R is positive, I must have the same sign as V. Therefore your current will increase.

Current flowing through a device depends on resistance offered by that device.

The only preventive maintenance that can be done to electric motors by maintenance personnel is to disassemble the motor. The motors bearings can be cleaned and re greased or if sealed bearings that can be changed out for new ones. Remove any grease or dust build up from the stator with compressed air. The stator then should be washed out with a solvent that is specifically made for cleaning electrical equipment. Dry the stator making sure that the motor coils have room around them for air to flow. Dirt accumulations around coil wiring insulation is the biggest cause of motor failure. The coil wires need cooling air moving across them. With totally enclosed motors the cooling vanes on the outside of the motor need to be kept clean as they are the only means of removing the heat from the motor.

If you are questioning about different relay (contactor) constructions, the terms moving coil and moving iron designate what part of the relay moves and carries the conductor that makes or breaks a circuit.

Bridge diodes are generally used in a bridge rectifier to convert AC into DC.

Relays which operate on 220 to 240 Volts are available. There are many different types, from miniature ones made for use in electronic equipment and printed circuit boards, to large ones made for use in electrical appliances and industrial equipment.

When you describe a relay you must define several things: its operating voltage; the number of switch-poles that it has; the current-carrying capacity of its contacts when switching either direct or alternating current; the method of connecting it into a circuit - solder posts for wiring or for printed circuits; spade terminals or a "relay plug base" - and finally the type of working environment in which it is to be used.

Relays made for use in dry "instrument case" conditions are built differently from relays which are made for use in damp conditions such as household washing machines or dishwashers. Relays are also specially made to withstand the wet and dirty conditions found in factories, coal mines or on board ship.

Relays having contacts capable of carrying and switching currents in excess of 25 Amps are called "contactors".

Ohm's Law: voltage is current times resistance, so 8 amps times 2 ohms is 16 volts.

it burns

Current density is the amount of electrical current flowing in a unit of cross sectional area of that conductor. You'd look at the current flowing and the cross sectional area of the conductor and make a calculation from that. All you need do is decide on what unit of cross sectional area you wish to use. In wire, we usually use mils. Use the links below for more information.
Density current is the measure of the density of flow of a conserved charge

CAPACITOR

Explanation:

An interesting property of capacitors is that they will block DC after they become charged, but will (for the most part) allow AC to flow through. When a capacitor is fully discharged, DC can flow through it freely, but as it is doing so, the cap is gradually becoming charged. Finally, when it has reached its storage limit, the cap will not allow any more electricity to flow through it, and will act as a blocker on the circuit. This can be observed if you simply wire a capacitor in series with a simple circuit connecting a battery to a light. When the circuit first comes on, the light will turn on, but after some time (when the cap becomes fully charged) it will turn off. Exactly how long it takes this to happen depends on the capacitance of the cap; With very low-capacitance caps, it will probably happen faster than your eye can perceive, but it still will happen. If you remove the battery and simply leave the cap connected to the light, the light will turn on again as the cap flows into itself, acting like a battery, and the light will stay on until the cap fully discharges. So a cap blocks DC; If you think about it for a moment, you should be able to understand why they allow AC to pass through: AC keeps reversing its polarity. As long as the AC switches fast enough to prevent the cap from becoming fully charged in any direction, then the cap will partially charge in one direction, and as the AC polarity reverses, the cap will start to discharge, then charge in the opposite direction. Very low-capacitance caps may partially block the AC because they become fully loaded before the AC cycle is complete, however. TOO many words for an explanation yes it block DC and it acts as a storage of energy. charged or not charged it will block dc IF THE DC changes then more or less it will pass this levels because varying DC is AC after all,

In a perfect inductor (one with no series internal resistance), the current lags the voltage by 90 degrees. If the inductor has series internal resistance, then the current will lag the voltage by less than 90 degrees - the more the resistance in series with the inductor, the smaller the angle. The tangent of the angle can be found from the ratio of the inductive reactance of the inductor to the DC resistance of the inductor.

That is, Tan (phase angle) = (2 x pi x frequency (Hz) x inductance (H)) divided by resistance (ohms)

eg, a 1 henry, 100 ohm inductor on 60Hz would give:

(2 x pi x 60 x 1) / 100 = 3.77; tan-1(3.77) gives 75 degrees lag of current behind voltage.

The cosine of this angle gives the 'power factor' for the inductor - that is, the amount of useful energy dissipated in the inductor. Cos 75 is about 0.25 - so 25% of the energy actually does useful work (heat) - the rest of the energy (75%) is returned to the supply mains when the inductor discharges its magnetic field.

Without going into the math, the change in speed increases the torque the motor can supply. The further the motor speed and supply speed are apart (known as the slip), the greater the torque will be.

It depends on the device, if for instances the machine is a pc, laptop mobile phone charger or anything that has a modern switch mode power supply built into it then you can use it on anything between 110 and 240, it will auto select, i don't recommend attaching a machine that is rated at 240v to a 460v supply, you will need to contact the manufacture to determine operating parameter's.

a circuit breaker trips on overload,if this breaker has tripped many times it may be worn out,if there is a overload happening the breaker is doing it s job keeping you safe.Main breaker needs to be replaced when your meter has been pulled(removed from metersocket)Have a electrician look at it and verify problem, you should not attempt to change out yourself it will be live.......

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