# electromagnetism

## right hand rule

The direction of the magnetic field created when current flows through a wire depends on the direction of the current. A simple rule, called the right hand rule, makes it easy to find the direction of the magnetic field if the direction of the current is known. The rule is illustrated in the Figure 1.1. When the thumb of the right hand is pointing in the same direction as the current, the fingers of the right hand curl around the wire in the direction of the magnetic field. Click image to the left or use the URL below. URL:

## uses of electromagnetism

Electromagnetism is used not only in a doorbells but in many other electric devices as well, such as electric motors and loudspeakers. It is also used to store information on computer disks. An important medical use of electromagnetism is magnetic resonance imaging (MRI). This is a technique for making images of the inside of the body in order to diagnose diseases or injuries. Magnetism created with electric current is so useful because it can be turned on or off simply by turning the current on or off. The strength of the magnetic field is also easy to control by changing the amount of current. You cant do either of these things with a regular magnet.

## what is electromagnetism

Electromagnetism is magnetism produced by an electric current. When electric current flows through a wire, it creates a magnetic field that surrounds the wire in circles. You can see this in the diagram below. Note that electric current is conventionally shown moving from positive to negative electric potential, as in this diagram. However, electrons in current actually flow in the opposite direction, from negative to positive potential. Q: If more current flows through a wire, how might this affect the magnetic field surrounding the wire? A: With more current, the magnetic field is stronger.

## instructional diagrams

No diagram descriptions associated with this lesson

## questions

the field described in question 2 runs parallel to the electric wire.

``````a. true

-->  b. false
``````

the direction of the field described in question 2 depends on the currents

``````a) voltage.

b) resistance.

-->  c) direction.

d) none of the above
``````

the strength of the field described in question 2 depends on the amount of current flowing through the wire.

``````-->  a. true

b. false
``````

devices that use electromagnetism include

``````a) doorbells.

b) electric motors.

c) loudspeakers.

-->  d) all of the above
``````

## diagram questions

No diagram questions associated with this lesson