# Physics

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Power transmission lines often use a form of electric current called alternating current, but in many regions, such as the Province of Quebec, high-voltage direct-current lines are used instead. Direct current is the kind of electric current you are studying in this chapter. A certain direct-current power transmission line has a resistance of 0.255 Ω/km. 812 kV of potential drives the current from the generating station to a city located 125 km from the plant. What is the power loss due to resistance in the line?

• Physics -

Rt = 0.255 Ohms/km * 125km = 31.875 Ohms. = Total rewsistance.

Pl = I^2 * Rt = I^2 * 31.875 = Pwer lost.

The power loss is proportional to the square of the current. Therefore, if we don't know how much current is flowing; we can't calculate the power loss.

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