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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
Why size of hv transformer is small?
Most people would agree that hv transformers, if that means transformers for over 1000 v, are never small.
The size of a transformer is determined by physical limits. The iron-based magnetic core of a transformer is a material with a limit to the permitted flux-density allowed if losses are to be kept to a reasonable level. Therefore the core size is determined by the maximum magnetic flux required, whch in turn sets the volts-per-turn figure for the windings.
The current in the windings is set by the size of wire used, which depends on the number of turns required. A large core allows fewer turns for a given voltage, therfore thicker wire can be used. Therefore a larger core allows thicker wire and more current.
Thus the size of a transformer is set by its power-handling requirement. HV transformers are increased in size by the need to maintain adequate insulation on the high-voltage windings.
What are the three types of motor skills movement?
The three types of motor skills movement are Gross Motor Skills, Fine Motor Skills, and Balance and Coordination.
What is a compound dc generator?
generators are machines that convert machanical energy to electrical energy and could be AC or DC. if in a DC generator has it field armature connection in both series and parallel its said to be compound dc generator.
AF means audio frequency. Audio Amplifiers can be subgrouped as voltage amplifiers (or pre-amplifiers) and power amplifiers. The voltage amplifier will raise the level of level of the output of a microphone from say 1 mV to 500mV or 1V. The power amplifier will be the interface between this and the load, which is a speaker. The resistance of the speaker is often 4 ohm or 8 ohm. You cannot have a speaker with 1k as resistance! As such to get say 8W output, an amplifier providing 8V will have to pump 1 amp into an 8 ohm speaker. Thus power amplifiers will have to drive a lot of current into the load. Voltage amplifiers cannot do this. A power amplifier sometimes just has unity voltage gain, but has ability to drive a lot of current into the load.
Typical power amplifiers are operated in class B, where for 50% of the signal swing, one transistor provides current, and for the other 50%, the other transistor in a class B provides current into load. Class B amplifiers have cross over distortion, But this can be overcome by pre-biasing, or making the stage operate as class AB. The power amplifiers can also be used to power low resistance loads such as a step up transformer.
Can you use a potential divider for obtaining variable DC supply from a fixed AC supply?
The novel power supply for generating a constant d.c. voltage from a variable a.c. voltage supply line, includes a plurality of switch circuits (10, 12) which monitor voltage levels on respective secondary windings (L,M,H) of a power transformer and as voltage levels change, one of the plurality of switch circuits is selected to charge a capacitor (C1) which provides a range of d.c. voltages which are processed to provide the constant d.c. voltage.
A device with a overload protection used to control a motor is a?
A device with an overload protection used to control a motor is an Overload Relay.
Why is aluminum or copper wire not used as fuse wire?
Because those metals have a high meling point, so it's easier and safer to use fuse wire which melts at a lower teamp.
What type of test equipment would you use to check the resistance between motor winding?
Ideally megger test is the best test used to check the resistance of motor winding.
Where does hysteresis in a transformer depend on?
The power lost by hysteresis depends on the peak flux density in the core. If the transformer is getting hot even when on no load, it should be run at a lower voltage.
Can the surge protectors circuit breaker be reset an unlimited number of times?
Yes, the surge protectors circuit breakers can be reset an unlimited number of times.
What type of device is an Antenna ie analog or digital?
An antenna is analog it is not classified as being a digital device.
What size of cable is needed for 3.5KW shower?
The size of a cable needed for 3.5KW shower can range from 4.0mm.
Why do bulbs get dimmer in series circuits?
When light bulbs are connected in series circuits, they will get dimmer whenever a bulb is added. This is because the current is shared between all of the bulbs equally.
Answer
Lamps only operate at their rated power when subjected to their rated voltage. If you connect lamps in series, each lamp will be subject to a lower voltage, so they will not operate at their rated power and, so, will be dimmer. The more powerful lamps will actually glow less than the less-powerful lamps because their resistance is lower and the voltage drop across them will also be lower than the voltage drop across the less powerful lamps.
What is a time delay relay function used for?
A time delay relay is used in applications that have a need to be automatically switched on and off. A few applications that require time delay relays are strobe lights, stoplights, and Christmas tree lights.
Why the transfermer rating is in KVA where as generator rating is KW?
Transformers are rated based on the amount of current flowing through them, irrespective of whether the current is in phase with the voltage or not, thus KVA.
When it comes to generators, what the owner is interested in is how much real power the generator can deliver (watts). Most generators are rated at a specific real power and a power factor (often .95).
What is the difference between EMF and terminal PD?
An electromotive force is the potential differenceappearing across the terminals of a battery, generator, etc., when that device is not supplying any load. When the device is supplying a load current, the electromotive force is equal to the sum of the voltage drops around the complete circuit, including any internal voltage drop.
A potential difference (also known as a 'voltage'), as the name implies, is the difference in potential between two points.
A terminal potential difference is the potential difference appearing across the terminals of a voltage source, such as a battery or a generator, which varies according to the load supplied.
When the battery or generator is off load (i.e. no load is connected to it), the terminal potential difference is equal to the electromotive force of that battery or generator.
The terminal potential difference tends to decrease as the load current increases, due to a corresponding increase in the internal voltage drop of the battery or generator.
What is flush mounted electrical installation?
In this case, flush means even with. For example an electric box could be mounted on the outside of your wall and would be an eyesore. Flush mounting recesses the box inside the wall and provides a flush mount for the outlet cover plate.
Some more information is needed. 100% power factor for one hour and 220 volts = 22 kva. At 0.85 power factor = 22/0.85 = 25.88 kva
How much resistance must be placed in a 110 volt circuit in order to limit the current to 2 amps?
Ohm's Law: Resistance = Voltage divided by current
110 volts / 2 amperes = 55 ohms
Note: This represents 220 watts, which is a considerable amount of power for a resistor. In all likelihood, the resistance will change as a result of that amount of power (heat) so the end result, 55 ohms, is only valid as an absolute number, in that 55 ohms is the answer, but the cold value of the resistor is uncertain.
What is the leakage current of zener diode?
The leakage current of a (zener) diode is the current that leaks when a diode is connected in reverse biased.
