AC & DC ????????????

Question

Which is more powerful AC or DC at the same voltage?
If both have the same power, then why does the trains in India operate at 25000V AC while the Kolkata Metro (subway) operates at 750V DC ? Does that mean 25k V AC is equivalent to 750V DC ?

Answer 1

Voltage has little to do with power.

Voltage is energy (Volt = Joule/Coulomb)

Power is energy flow and is a product of voltage and current

P=V I (Watts = Joules/ sec)

AC is easier transmitted over long distances since it can be stepped up to a high voltage, transmitted and stepped down just before the consumer. High voltage AC is used for trains that run long distances. Local trains may employ DC. DC is 'safer' than AC, but that is another story.



No we can't say that "...25k V AC is equivalent to 750V DC " in terms of power since we don't know how much current is used in each case.

Answer 2

Electricity is electricity any way you slice it. The only difference between AC and DC is that one of them is an alternating current (60 pulses per second) and one is a direct current (continuous flow).



As far as the power question, you are confusing voltage with wattage. Watts = Volts x Amps. Wattage is the power output. If you have a 25000v system, regardless of AC or DC, and it is only using .00000001 amps, you are not going to have a whole lot of power.



A fantastic example of this is the spark plug or coil pack in your car. A spark plug is a very high voltage but low amperage to create a spark for ignition. Coil packs or distributors convert the low voltage high amperage charge from your battery into a very high voltage low amperage electricity.



Hope this helps :)

Answer 3

DC is more powerful due to it's constant frequency and magnitude Vs AC which is alternating or cycling.

Answer 4

interesting but needs a braineeeeeeeeeee to answer