如图,在通有电流强度为I₁的长直导线M附近,有另一段长为a的直导线N,N与M平行,相距为b,N中的电流强度为I₂.N受到的安培力大小为
Complete the following sentence with a (compound) word derived from the one(s) given in bracket.
Some experts ( ) believe that ancient Greece and Rome are vital sources of learning. (true)