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Electric Charge, Coulomb's Law, and Electric Fields

Terms you will need

  • electric chargeElectric charge is a property of matter that causes it to experience a force when near other charged matter. It is what makes things attract or repel each other in electricity.

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Electric charge, Coulomb's Law, and electric fields are fundamental concepts in understanding how charged particles interact and influence their surroundings. Electric charge is a property of matter that causes it to experience a force when placed in an electromagnetic field. Charges can be positive or negative, and like charges repel while opposite charges attract. Coulomb's Law quantifies the force between two point charges, stating that the force is directly proportional to the product of the charges and inversely proportional to the square of the distance between them. An electric field is a region around a charged particle where other charges experience a force. It is defined as the force per unit charge and is used to describe the influence a charge has on its environment. These principles are essential for analyzing and predicting the behavior of charged objects in various contexts, from simple electrostatic interactions to complex electrical systems.

Figures (8)

Diagram showing field lines and equipotentials around an electron, a negatively charged particle. In an electrically neutral atom, the number of electrons is equal to the number of protons (which are positively charged), resulting in a net zero overall charge
Electric field induced by a positive electric charge
Electric field induced by a negative electric charge
Coulomb's torsion balance
Figure 5.14 The electrostatic force F→F→ between point charges q1q1 and q2q2 separated by a distance r is given by Coulomb’s law. Note that Newton’s third law (every force exerted creates an equal and opposite force) applies as usual—the force on q1q1 is equal in magnitude and opposite in direction to the force it exerts on q2q2. (a) Like charges; (b) unlike charges.
Figure 5.15 A schematic depiction of a hydrogen atom, showing the force on the electron. This depiction is only to enable us to calculate the force; the hydrogen atom does not really look like this. Recall Figure 5.7.
Figure 5.16 The eight source charges each apply a force on the single test charge Q. Each force can be calculated independently of the other seven forces. This is the essence of the superposition principle.
Figure 5.17 Source charges q1q1 and q3q3 each apply a force on q2q2.

Charges come in two types: positive and negative. Like charges push each other away, and opposite charges pull each other together. This push or pull is described by Coulomb's Law, which says the force between two charges depends on their sizes and the distance between them.

The bigger the charges and the closer they are, the stronger the force. An electric field is the area around a charge where other charges feel this force. It shows how strong and in what direction the force would act on another charge placed there.

To picture it, imagine a charge as a source of invisible lines that show the direction and strength of the force it would exert on another charge nearby.

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