Define electric field, understand its physical significance, and calculate field due to a point charge and system of charges.
Defines electric field and its relation to force.
How do electric forces act across an empty space? To answer this, early scientists introduced the concept of a field.
A charge produces an electric field everywhere in its surrounding space. When a second charge (the test charge) is brought nearby, this field acts on it to produce a force.
Visual of electric field vectors around positive and negative charges.
For a positive source charge , the field points away from the charge. For a negative source charge , the field points towards the charge.
A point charge creates an electric field around it, directed along
The electric field is produced by the source charge . When a test charge is placed in this field, it experiences a force given by .
Calculates net electric field at three points.
Problem
Two point charges and , of magnitude and , respectively, are placed apart. Calculate the electric fields at points A, B, and C shown in Fig. 1.11.
(Note: Point A is the midpoint between the charges. Point B is to the left of . Point C is from both charges, forming an equilateral triangle.)
Calculate time of fall in an electric field.
Consider an electron falling from rest through a distance of in a uniform electric field of magnitude .
(Take and )
The field exerts a downward force on the electron with a magnitude of , where .
Using Newton's second law, the magnitude of the acceleration of the electron is , where (round to one decimal place).
Using the kinematic equation for a body starting from rest, the time required for the electron to fall this distance is , where (round to one decimal place).
MCQ testing that E is independent of q.
If the test charge used to measure an electric field at a specific point is doubled, what happens to the magnitude of the electric field at that point?