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## High school physics - NGSS

### Course: High school physics - NGSS>Unit 2

Lesson 3: Electric and magnetic fields

# Electric and magnetic fields

Review your understanding of electric and magnetic fields in this free article aligned to NGSS standards.

## Key terms

TermMeaning
FieldA field models what an object would experience related to a force at a given point in space.
Magnetic FieldA magnetic field is a field explaining the magnetic influence on an object in space.
Electric FieldA electric field is a field defined by the magnitude of the electric force at any given point in space.
CurrentCurrent is the rate of charge moving past a region.

## Forces at a distance and fields

Forces at a distance, such as gravitational, electric, and magnetic forces, can be represented using vector fields. These fields describe a relationship a given object might experience to the forces at any point in space.
Fields are often represented in two dimensions using field lines. The density of these field lines indicates the strength of the field at a particular point - the more dense the lines, the stronger the field. The conventions for how to show gravitational, electric, and magnetic field lines are all slightly different to model the unique aspects of each force. Some common models are shown below.

## Electric fields

Electric fields arise from electric charges and changing magnetic fields.
An electric charge, or a collection of charges, will have an associated electric field. Any charged object placed in this field will experience an electrostatic force as the field interacts with the charge of the object. Field lines represent the force a positively charged particle would experience if it were in the field at that point.
A changing magnetic field can also cause electric charges to move. This phenomenon is commonly used in electric generators to induce electric currents in wires. The induced current can be increased by causing larger changes in the magnetic field or by coiling the wire so that more wire is affected by the changing magnetic field.

## Magnetic fields

Magnetic fields arise from permanent magnets and electric charges in motion.
Magnets can occur naturally (such as the Earth’s magnetic field), or they can be made by magnetizing ferromagnetic materials.
Magnetic fields ultimately are the result of the motion of charges. A typical representation of this can be seen in the figure below. We can see the magnetic field surrounding the straight wire as current is moving through it. We use this phenomenon to run motors and even to store information in computers.
The magnetic field around a current-carrying wire can be increased by coiling the wire or increasing the current running through it. In a magnetic field, the field lines represent the force the north side of a magnet might experience if it were in the field at that point.

## Want to join the conversation?

• Does the earth have a magnet inside?
• earth as a whole is a magnet
• why do moving charges cause an magnetic field?