Welcome to this tutorial on the direction of the electric field for positive charge and negative charge. Our previous article explained how to calculate the force between two charges using Coulomb’s Law.
We know that electric charges are of two types
- Positive charges and
- negative charges
To find the direction of the electric field of any charge $Q$, we have to bring a positive test charge $q_0$ near that charge.
Here it is important to note that a test charge is a charge of such a small magnitude that it has little or no impact on the field surrounding the point where it is placed.
When the test charge is brought close to the charge Q, the direction in which it experiences force is considered as the direction of the electric field due to that charge.
Direction of electric field for positive charge
Consider a scenario where we have a positive charge $+Q$, and we are bringing a test charge $q_0$ into the field of this charge. So, $+Q$ is our source charge producing the electric field, and $q_0$ is our test charge for testing the electric field.
The force on test charge $q_0$ due to a positive source charge $+Q$ acts in an outward direction, as shown in the figure. This is due to the fact that like charges repel each other.
If we move the test charge to another point in the field of our source charge, the force acting on it will always be repulsive and in a radially outward direction.
As a result, the direction of the electric field generated by a positive source charge will always be radially outward direction.
The diagram below illustrates the electric field of a positive charge.
Direction of electric field for negative charge
Again consider a scenario where we have a negative charge $-Q$, and we are bringing a test charge $q_0$ into the field of this charge. So, $-Q$ is our source charge producing the electric field, and $q_0$ is our test charge for testing the electric field.
The force on the test charge $q_0$ due to a negative source charge $-Q$ acts in an inward direction, as shown in the figure. This is due to the fact that unlike charges attract each other.
If we move the test charge to another point in the field of our source charge, the force acting on it will always be attractive and in a radially inward direction.
As a result, the direction of the electric field generated by a negative source charge will always be radially inward direction.
I’ll say it again, test charge will always be positive, so don’t forget that. The diagram below illustrates the electric field of a negative charge.
