An electric field is the influence of an electrically charged object on other charged bodies. The field is infinite but decreases with distance according to the inverse square law. The field’s direction and magnitude depend on the type of charge. The force experienced by a charged object in an electric field can be calculated using F=Eq. Electric field lines are drawn conventionally with arrows pointing away from positive charges and towards negative charges. Quantum electrodynamics explains the exchange of photons in charged object attraction and repulsion.
An electric field can be thought of as the sphere of influence of an electrically charged object. Anything that has an electric charge will affect and be affected by other charged bodies. If two charged objects are placed close enough to each other, each will experience a measurable force acting on it. The field is theoretically infinite in extent, but its size decreases with distance from the source according to the inverse square law. This means that if the distance is doubled, the strength of the field is divided by four, and if the distance is three times, the strength is divided by nine, and so on; the field then becomes negligible at large distances.
Since an electric charge can be positive or negative, the electric field is a vector field, which means it has a direction as well as a magnitude. Two electrically charged objects will experience a repulsive force if they have the same type of charge and an attractive force if they have different types of charge. The force experienced by a charged object in an electric field can be calculated as F = Eq, where F is the force in Newtons, E is the electric field in volts per meter (v/m), and q is the charge in Coulombs. This equation can be rearranged to give the field strength, E, in volts per meter: E = F/q. These examples apply to small, point-like objects; for more complex, or multiple, charged bodies, the calculations are more complicated.
The direction of an electric field is defined as the direction in which the electric force would be felt by a positively charged object placed in the field. Therefore, the field would point away from a positive charge and toward a negative charge, as like charges repel and dissimilar charges attract. In the case of two bodies with the same type of charge, each would experience a force – calculable from the equation F = Eq – directed away from the other object. Conversely, for two oppositely charged bodies, each would experience a force directed towards the other object.
An electric field line can be drawn with an arrow pointing away from a positive charge and pointing towards a negative charge. Thus, a positively charged object would be depicted with field lines pointing away from it in all directions, and a negatively charged object with field lines converging on it. This, however, is just a convention and does not indicate that there is anything physical pointing in any particular direction.
The concept of electric field described above is part of “classical” physics. The classic description works well for everyday applications, but doesn’t explain what’s actually happening when charged objects attract or repel each other. A branch of quantum theory known as quantum electrodynamics (QED), attempts to do this in terms of the exchange of photons, the carriers of the electromagnetic force.
Protect your devices with Threat Protection by NordVPN
