Answer:

where E = electric field intensity
Explanation:
As we know that plastic ball is suspended by a string which makes 30 degree angle with the vertical
So here force due to electrostatic force on the charged ball is in horizontal direction along the direction of electric field
while weight of the ball is vertically downwards
so here we have


since string makes 30 degree angle with the vertical so we will have





where E = electric field intensity
B is the answer, I’m really good at this subject
Solution
Let a cell of emf E be connected across the entire length L of a potentiometer wire . Now , if the balance point is obtained at a length l during measurement of an unknown voltage
.
The balance point is not on the potentiometer wire - this statement means that
. In that case ,
l > L
V > E
The heat energy released from a piece of wire or any other section of a circuit is:
Energy = (voltage between its ends) x (current through it) x (time it's been going)