# Basic Question On AC & DC

Discussion in 'Homework Help' started by hitmen, Dec 22, 2009.

1. ### hitmen Thread Starter Active Member

Sep 21, 2008
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Why is the power pumped to our mains AC instead of DC?
I know that the DC power will "die out" but I am not sure of the reason why.

Apr 10, 2009
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In AC power .. the wire or cable behaves as of effective resistance whereas in
DC power only resistance only comes into effect...... The difference between the effective resistance and resistance can be understood by SKIN EFFECT.
So due to lack of skin effect in DC when compared to of AC the wires some time burns of due to high load in our mains/////

3. ### JDT Well-Known Member

Feb 12, 2009
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• AC is easier to generate - rotating magnets inside coils of wire.
• AC voltages can easy be converted to other voltages using transformers (high voltages are needed for long-distance transmission).
• AC allows the use of simple electric motors (induction motors).
• Because AC voltage drops to zero twice every cycle, switches and circuit breakers are much easier to design.
• Allows the use of inductive ballasts for lighting.
• The frequency carries an accurate timebase for metering and clocks.
There are one or two disadvantages but totally outweighed by the advantages.

Edison did not get everything right!

4. ### Wendy Moderator

Mar 24, 2008
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The big answer is something JDT already said, transformers. Transformers are simple, low tech components, but they can have better than 95% (some cases 99%) efficiency converting voltages.

The second part is resistance of the wires. With high voltages (extremely high in high tension lines) the current is way down compared to the wattage being transmitted. This means the wires carrying the current drops less voltage (Ohm's Law, but resistance is a constant in this equation). Any voltage drop in the wires is pure waste. When the current gets to it's destination, it is converted down to a safe voltage (and the equivalent current goes up for the same wattage).

Feb 28, 2009
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