A planet in 7th sign from its Exaltation sign is with only 5% power. A planet 180 degrees from its exaltation degree is without power as shown in following chart.

Mer 15 Sat 20    
      Mar 28
Jup 5      
  Moo 3 Sun 10 Ven 27

The numbers are degrees. For eg. 15 is 15th degree.