I don't understand the grass seeds demo (41:00). Why did they produce field lines?
Lecture 2

Let me elaborate further, the prof had a container with grass seeds and oil (the oil was simply there to allow the grass to move/rotate freely). Near the centre, there were two charges about 3 cm apart. The charges were equal in magnitude and were both positive. They caused the grass seeds to rotate such that they created the same electric field drawings the prof drew for that field configuration.

Question

I don't understand the grass seeds demo (41:00).  Why did they produce field lines?
Lecture 2

Let me elaborate further, the prof had a container with grass seeds and oil (the oil was simply there to allow the grass to move/rotate freely).  Near the centre, there were two charges about 3 cm apart.  The charges were equal in magnitude and were both positive.  They caused the grass seeds to rotate such that they created the same electric field drawings the prof drew for that field configuration.

anonymous · Answer

Just kidding I get it now.