What is the main advantage of using per unit system?

In the following power system, power flow solution will determine how many main unknowns? PS(2).png

A transmission line has the following parameters: z=0.02+j0.33 S/km y=j4.7×10-6 S/km Length=300 If sending and receiving end voltages are 500kV, what is its maximum theoretical real power transmission capability? 

In the following power system, if V2∠δ2= 0.9717∠-2.7o , what is the real power loss on Line 12? (Sb=100MVA) PS(2).png

In 1957, Republican President Dwight D. Eisenhower federalized local National Guard troops to enforce the desegregation of: A) Little Rock High School B) Louisiana State University C) University of Alabama D) Mississippi State 

True or False. Prior to his election as Vice-President in 1960, Senator Lyndon Baines Johnson of Texas had usually supported segregation laws in the South.   A) True B) False 

In the 1940s, the new federal agency called the _?_, conducted investigations into racial discrimination against African-Americans who applied to work for federal government contractors. A) the FEPCB) the NAACPC) the SCLC  D) the HBCU

In the case of Plessy v. Ferguson (1896), the Supreme Court ruled against Homer Plessy, who was charged with breaking segregation laws in the city of:A) MobileB) ShreveportC) New OrleansD) Montgomery

The 13th Amendment to the Constitution: A) abolished slavery nationwide B) guaranteed equal protection under the lawC) granted the right to vote to male citizensD) abolished the poll tax

When Abraham Lincoln ran for president in 1860, he promised:  A) to abolish slavery, nationwide B) to halt the spread of slavery to the WestC) to put the issue of slavery to a national vote  D) to abolish slavery in the Southern states