"The number of magnetic lines of force passing through any area in a magnetic is known as magnetic flux" So the definition of flux goes. But I find it rather ambiguous and loose. Or is that I am missing some vital point? The magnetic lines of force are not real, they are imaginary lines of force which we draw using a north pole. We can draw as many as we desire using a different starting point for our drawing of lines of force. (Of course, we say that we say that when the strength is more we draw the lines closer and when it is less, we draw them sparse, but it is still subjective, one can start at a different point and draw as many lines as he wants.)SO how can we depend on the number of lines for the definition of flux? Is there no better definition? We can straight forward define it as B.dA perhaps which is less ambiguous.