We have all come across the impacts of electricity in our daily lives, from the spark that appears when we touch a doorknob to the operation of our cell phones. An unseen force known as the electric field is responsible for these events.
What is an Electric Field?
An area surrounding a charged object where other charges experience force is called an electric field. A little charge, known as a test charge, will exert an attraction or repulsion on another charged object when it is placed close to it. The space where this force occurs is known as the electric field, and it occurs without any contact.
Consider it this way: a charged object generates an electric field around it that pushes or pulls other charges, much like the Earth produces a gravitational field that pulls objects downward.
Electric Field Definition
The force (F) that a small positive test charge (q) experiences at a given location is divided by the charge’s magnitude to determine the electric field (E) at that location.
Electric Field, E = F / q
E is the electric field (in N/C – newtons per coulomb)
F is the electric force on the test charge
q is the magnitude of the test charge
The force acting on a positive test charge is assumed to be in the same direction as the electric field.
Electric Field Due to a Point Charge
Suppose, we have a charge Q placed at a point in space. The electric field it produces at a distance r from it is given by:
E = 1 / 4πε0 ⋅ Q / r2
Here,
ε0 is the permittivity of free space (a constant),
Q is the source charge,
r is the distance from the charge to the point where the field is being measured.
This formula tells us that the electric field:
Increases if the charge increases.
Decreases with the square of the distance.
This is similar to how gravity behaves the farther you are from the source, the weaker the field.
Electric Field Lines
Electric field lines are used to show electric fields. These are fictitious lines that indicate the electric field’s strength and direction.
Key features of electric field lines:
They end on negative charges after beginning on good charges.
The field is stronger when the lines are closer together.
Lines don’t ever intersect.
At any given point, the field’s direction is tangent to the line.
This clarifies the interactions between charges. For example, the field lines exhibit attraction between a positive and a negative charge. The field lines exhibit repulsion between two like charges.
Superposition Principle
The vector sum of the fields caused by each charge is the electric field at a place if there are several charges. We refer to this as the superposition principle. All we have to do is sum up the electric field vectors caused by each charge, taking into account both direction and magnitude.
Importance of Electric Field
It helps explain:
How capacitors store energy.
How electric circuits work.
The behaviour of electrons in electric and magnetic fields.
Many practical technologies, like touchscreens, photocopiers, and more.
Physical significance of electric field:
Electric field is a characteristic of the system of charge. It is independent of the test charge that we place at a point to find the field.
Since force is a vector quantity so electric field is also a vector quantity.
Effect of any motion of q1 on charge q2 cannot arise instantaneously. The accelerated motion of charge q1 produces electromagnetic waves, which then propagate with the speed of light c, reach q2 and cause a force on q2.
Electric field can be detected only by the effects (forces) on charge. It has an independent dynamics of its own. Electric field can also transport energy.
Summary
How charges interact over distances is made easier by the electric field notion. It’s a fundamental concept that links several branches of science and common technology.
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