Why is electricity generated as alternating current and not as DC?

2 Answers
Jun 9, 2017

This is not true

Explanation:

We have both AC and DC generators which generate AC and DC current , both run with same mechanism but differ by just , that DC generator uses split rings but ac uses slip rings . for more details you can see a proper demonstration on YouTube .

Jun 9, 2017

The main reason is that the voltage of Alternating Current can be "stepped up" for long distance distribution and then "stepped down" for local distribution, using transformers.

Explanation:

I believe that you are asking; "Why is Alternating Current commonly used by Electric Companies to provide electric energy to their customers?"

Here is an example:

Let's assume that you are a power company and you have chosen to use DC:

1 mega-Watt industrial load (#440# Volts DC @ #~2300# Amperes)

10 kilometers away from the power generator and the resistance of the power lines are #0.1 Omega/"km"#

The loss of the power by the 2 power lines (one for + and the other for the -) is:

#P_"loss" = 2(2300"A")^2(10"km")(0.1Omega/"km")#

#P_"loss" ~~ 10# mega-Watts

The voltage drop on the power 2 power lines #4600# Volts

This means that your generator voltage is #5040# Volts and it must generate #2300# Amperes. You generate 11 mega-Watts to deliver 1 mega-Watt.

Consider the same problem with AC and you can step-up to 250,000 volts for distribution and step-down at the load:

1 mega-Watt industrial load (#440# Volts AC @ #~2300# Amperes)

We step up the voltage to 250,000 volts for distribution:

#P = (440"VAC")(2300"A") = (250000"VAC") (x"A")#

#x = ((440)(2300))/250000#

#x ~~ 4"A"color(red)(larr "This is the current in the distribution lines")#

10 kilometers away from the power generator and the resistance of the power lines are #0.1 Omega/"km"#

The loss of the power by the 2 power lines (one for + and the other for the -) is:

#P_"loss" = 2(4"A")^2(10"km")(0.1Omega/"km")#

#P_"loss" ~~ 32# Watts

The choice between losing 10 million Watts to deliver 1 million Watts or losing 32 Watts to deliver 1 million Watts to a customer is simple. That is why power companies use AC.