# Electricity: Electric Fields

## Electric Fields

• An electric field is a region around a charged object where the charge can exert an electrical force on another charged object.

• Field lines extending away from a charged object represent its electric field, providing a visual way of showing the field’s direction and strength.

• The field strength (or electric field strength) is the force per unit charge. The most potent field is near the charged object, with field strength reducing further away.

• A positive charge placed in a field will experience a force in the direction of the field, whilst a negative charge experiences a force in the opposite direction.

• The principle of superposition in electric fields means the total electric field strength at a point is the vector sum of the electric field strengths due to each individual charge.

## Properties of Electric Fields

• When two charged objects are in close proximity, their fields interact. If two similar charges, both positive or both negative, are in close range, the fields will repel. If the charges are opposite, one positive and one negative, the fields attract.

• Field lines never cross. Each point in an electric field can only have one direction of force.

• Electric field lines are always continuous, extending from positive to negative charges and from positive charges to infinity.

• The density of field lines represents field strength. Regions with closely packed lines indicate a stronger field than areas where field lines are spaced farther apart.

## Phenomena in Electric Fields

• Lightning is a real-world example of electric field phenomena. The ground becomes positively charged while the storm cloud above becomes negatively charged, creating an enormous electric field between them. Once the electric field becomes large enough, it can ionise the air and create a conducting path for lightning.

• Static electricity is another example. By rubbing materials together, electrons can be transferred, resulting in positive and negative charges. The separating charge creates an electric field, which can cause smaller lighter objects to be attracted or repelled.

Knowledge of electric fields underpins our understanding of atomic structure and how charged particles interact in an electric field. Quizzes, practice questions, and diagrams are recommended to consolidate your understanding of this topic.