Question

Problem 9:   The hydroelectric generators at the Hoover Dam can produce a maximum current of 8.00 × 10³ A at 250 kV.

Part (a) What is the maximum power output of the generators, in watts?

Pmax=_____

Part (b) The water that powers the generators enters and leaves the system at a low speed (thus we can neglect its change of kinetic energy) and loses 160 m of altitude during the process. What is the water flow required, in cubic meters per second, to produce this power, assuming 71 % efficiency?

R=______

Problem 11:   A particular aluminum transmission line has a resistance per length of 0.066 Ω/km. Assume aluminum has a resistivity of 2.65 × 10^-8 Ω⋅m and a density of 2.70 × 10³ kg/m³.

Part (a) What is the mass of one kilometer of this line, in kilograms?

mA1=______

Part (b) What is the mass, in kilograms per kilometer, of a copper line having the same resistance as the aluminium one? Copper has a resistivity of 1.72 × 10^-8 Ω⋅m and a density of 8.90 × 10³ kg/m³.

mCu/L=______

Answer 1