Electrical Engineering

the resistance of the inside layer

silver is good

the amount of radiating surface

bigger is better

Voltage commutation: This is possible in ac circuits...The thyristor gets turned off by reverse bias (negative half cycle) voltage applied across it. This is also called line commutation.

Current Commutation: This is possible in dc circuits ...This type of commutation makes use of auxiliary circuit which contains inductor,capacitor,diode and even a thyristor(auxiliary). This is called Forced commutation.

If a 100 ohm 1 watt resistor and an 800 ohm 2 watt resistor are connected in series, the maximum DC voltage that can be applied without exceeding the power limit of both resistors is 45 volts.

Start with power rule and ohm's law...

P = IE

E = IR

so

P = I2R

solve for current

I2 = P/R

I = (P/R)0.5

determine current at max power for each resistor R1 = 100, R2 = 800

I1 = (1/100)0.5 = 0.1 amperes

I2 = (2/800)0.5 = 0.05 amperes

The limiting resistor is R2, so calculate voltage of both at current flow of I2

V1+2 = (0.05)(900) = 45 volts

If the heater is rated as a 3 phase 480 volt heater then a neutral is not needed. If the voltage stated is 277 volts three phase then a neutral is needed.

Yes it is constant at Zero Frequency.

No, DC or Direct Current only means that the current only goes one direction, but it can have a frequency. You can have a square wave, sawtooth wave or sine wave that never goes from positive to negative or negative to positive and it would be a direct current with a frequency.

Ampacity must be derated depending on the number of conductors and the ambient temperature. In the Canadian Electrical Code Table 5C denotes derating for the number of conductors.

1-3 conductors = 100% load

4-6 conductors = 80%

7-24 conductors = 70%

25-42 conductors = 60%

43 or more conductors = 50%

There is no need to. The manufacturer designed the appliance for the specification of not needing a ground to be connected to it.

A CT is a current transformer, used to measure current flow in a conductor. Neutral is power return, usually grounded at the distribution panel. A neutral CT, then, is a device that measures the current flow in the neutral conductor. In a three phase star system, each phase returns current to neutral, but the three phases cancel each other out, resulting in effectively zero current in neutral. The neutral CT is used to detect an imbalance in the system, perhaps caused by a ground fault or by some failure in one of the phase loads. In a single phase, single ended system, there is current on neutral, so the value of a neutral CT is not so great. If you also had a hot CT, you could compare and detect imbalance between hot and neutral, which would be an indication of a ground fault. (Actually, a ground fault current interrupting device, also called a GFCI, usually compares current in hot and neutral simultaneously, because both conductors are wound together as the sensing transformer primary - any perceived current is a ground fault.) In a single phase, double ended system, such as the 120/240 split phase system used in the US, a current CT could indicate ground fault or a system imbalance but, usually, imbalance might be a normal situation as various loads are turned on and off.

negative ground systems have always been in use but some chose to use positive grounds as wires were poorly insulated and suffered from corrosion on negative earth systems but positive earth systems did not suffer as badly to corrosion (i heard somewhere Henry ford came up with the positive ground idea cant say for sure)

in recent times insulation is greatly improved and with bridge rectifiers instead of contact rectifiers which caused more uneven power flow to the battery most decided to use the same system putting everything on negative ground for simplicity but you will always have one oddball who uses positive ground just for the sake of being different

Galvanic- a constant and direct current, having a positive and negative pole and produces chemical changes when passing through the tissues and fluids of the body

Telsa High Frequency current- heat producing current with a high rate of oscillation or vibration

It is the space within the intestine

A form Z relay contact is one of six common types of contact configurations. A type Z is a single pole, double throw, double break configuration. There is no common hot terminal. It is usually used where two separate circuits need to be opened at the same time.

HT drives are the pumps or motors operate at more power typically more than 0.5 Amps at 110 or 220 V DC whereas LT drives operate at lesser power less than 0.5 Amps at 24 V DC or 240 V AC.

If you ground the flow of current like the last part of your question states you will not have a complete circuit as the circuit will open on a short circuit. To make a complete circuit operate you need a power source, an overload device to protect the conductors of the circuit, conductors to carry the current and a load across the power source which causes the current to flow in the circuit.

Leave any one of these things out and you will not have a complete circuit.

If the nameplate states 20 amps then that is the full load amperage when the motor is running. The start up current on the motor could reach 300% of the FLA depending on the type of motor and the load that is connected to the motor.

They visually identify which fuse has operated.

The electrical code states that a 7.5 HP 460 volt three phase motor draws 11 amps. For fuse sizes, non time delay - 30 amps, time delay type D - 20 amps and if using a breaker it will be 30 amps. Minimum wire size is #12 and the maximum setting of overload devices will be 13.75 amps

A generator needs to have residual magnetism in its field coils to start the generation of electricity. A generator that has not been run in a long time will loose this magnetism. Because the field voltage is a DC supply, a battery across the field wiring will energize the coils instantaneously. Doing this several times will cause sparking when the contact to the battery is broken, hence the flash. This intermittent energizing and de-energizing will bring the residual magnetism back into the field coils. When the generator is started, the voltage output should rise to its normal level. If it does the magnetizing of the field coils to bring back the residual magnetism will have worked.

If you are working with a coil, you should have all parts of the coil and knowledge to work with them. In the related links box below, I posted a websited which has all this knowledge and another one about builduing the tesla coil.

Cables under oceans varies from 2 Gbit/s to 10 Tbit/s

Single phase voltages vary throughout the world. To answer this question a basic voltage or country voltage has to be stated.

Because that's the definition of Ohm's law. Current = voltage / resistance.

Here's one way to think about it. Resistance is the degree of difficulty in moving charge from one place to another. If you increase that resistance, it is harder to move the charge. Current is rate of flow of that charge, hence current goes down.

The importance of the Transistor was that it could amplify an electrical signal.

It was thus an analog of the vacuum tube devices, and could take advantage of the circuit history and applications that had built up over the preceding 50 years.

Depends on manufacturer..Normally the ratings are as follows

1. Service short circuit breaking capacity is 7.5 kA

2. Rated short circuit breaking capacity is 10 kA.