Electric Field Concept

Walk near a high-voltage transmission line holding a fluorescent tube, and it can glow faintly with no wire touching it and no switch flipped. Something is reaching across open air to push electrons inside the glass. That something is an electric field.

An electric field is the region around any charged object where another charge would experience a force. The field exists whether or not a second charge is there to feel it. It is measured in volts per meter (V/m) or equivalently newtons per coulomb, and it points in the direction a positive test charge would be pushed. Near a positive charge, the field radiates outward. Near a negative charge, it points inward. The field strength decreases with distance (following the inverse-square law from Coulomb's Law).

The field concept matters because it replaces the mysterious idea of "action at a distance" with a physical mechanism. Charges do not magically attract or repel across space. Instead, a charge creates a field, and the field exerts force on other charges within it. This same framework extends to electric circuits: a voltage source creates an electric field inside a wire, and that field pushes electrons through the conductor, creating current.

Worked Example

A Van de Graaff generator creates a uniform electric field of 3,000 V/m between two parallel plates separated by 10 cm.

• Understand the setup. The field pushes any positive charge from the positive plate toward the negative plate.
• Calculate the voltage across the gap. Voltage = field strength x distance = 3,000 V/m x 0.1 m = 300 V.

If you placed a proton in this field, which direction would it move?

Toward the negative plate. The field pushes positive charges in its own direction (from high voltage to low voltage). An electron would move the opposite way, toward the positive plate.

Electric fields are the invisible mechanism behind every circuit, every capacitor, and every lightning bolt.

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