Class 12 Physics (CBSE)

Electric Charges and Fields

How can a simple plastic comb bend a stream of flowing water without ever touching it? The answer lies in an invisible, silent force field that wraps around every charged particle in the cosmos.

At the heart of this mystery is electric charge, a fundamental property of matter. It comes in exactly two opposite flavors: positive and negative.

The golden rule of electromagnetism is simple. Like charges aggressively push each other away, while opposite charges pull together.

But how do they exert forces across empty space without touching? To explain this, Michael Faraday proposed that every charge creates an invisible 'electric field' around itself.

Think of a positive charge as a fountain. It constantly radiates field lines outward in every direction, showing the path a positive test charge would be pushed.

A negative charge behaves as the exact opposite—a sink. Its field lines point directly inward, pulling positive test charges toward it.

When a positive and a negative charge are brought near each other, their fields merge. The lines curve gracefully out from the positive fountain and loop directly into the negative sink.

How strong is this invisible force? Coulomb's Law tells us that the force is proportional to the charges multiplied, divided by the square of the distance between them.

To find the strength of the electric field itself at any point, we measure the force felt per unit of a small positive test charge.

Watch out for this common mistake: field lines are a map, not physical ropes. Because they show the net direction of force, field lines can never cross each other.

Remember: charge creates the field, and the field exerts the force. Next time you see static electricity, you are seeing this invisible geometry in action.