electromagnetism

LEARNING OBJECTIVES

By the end of this lesson you should be able to:

• Define electromagnetism.
• Describe electromagnetic force.
• Explain Fleming’s rule.
• Describe the properties of electromagnetic waves.
• Describe the application of electromagnetism.

Electromagnetism refers to a branch of physics that is concerned with the study of electromagnetic force. The electromagnetic force is among the major forces and it exhibits electromagnetic fields like electric fields, light, and magnetic fields. For example, when current, that is, positive charges are moving in a wire, a magnetic field is produced along the wire. The electromagnetic force is a kind of physical interaction that happens between electrically charged particles. The electromagnetic force is the main reason why the electron and the nucleus of an atom are bound.

Electromagnetic force refers to a type of physical interaction between charged particles (electrically). This force is a combination of magnetic and electrical forces and it occurs between charged particles. The electromagnetic force can either be repulsive or attractive.

Electromagnetic induction refers to the principle of generation of voltage or electricity when a conductor is moved through or placed in a magnetic field. The voltage generated is dependent on the speed of the conductor through the electric field. The faster the conductor’s speed through the electric field, the greater the voltage or induced electricity.

How are electromagnetic waves propagated?

To propagate electromagnetic waves, you oscillate magnetic and electric waves at right angles to one another.

FLEMING’S RULE

Fleming’s Right-hand rule and Fleming’s Left-hand rule are important rules applicable to electromagnetism and magnetism. They are simple ways of working out directions of motion of electric current. These rules show the direction of three parameters (force, current, and magnetic field).

FLEMING’S RIGHT-HAND RULE

Fleming’s right-hand rule is applied to determine the direction of motion of the induced current. It states that if you arrange your thumb, forefinger and middle finger of your right hand, perpendicular to each other, your thumb points towards the direction of the conductor in the magnetic field, the forefinger towards the magnetic field direction, and your middle finger towards the induced current direction.

FLEMING’S LEFT-HAND RULE

It states that if you arrange your thumb, forefinger and middle finger of your left hand, then your thumb points towards the direction of the force of the conductor, the forefinger points towards the magnetic field direction, and the middle finger points towards the electric current direction.

DIFFERENCES BETWEEN FLEMING’S RIGHT AND LEFT-HAND RULE

Fleming’s left-hand rule	Fleming’s right-hand rule
It is applied in electric motors.	It is applied to electric generators.
The purpose is to find the direction of magnetic force in an electric motor.	The purpose is to find the direction of induced current acting in an electric generator.
The middle finger indicates the direction of the current.	The middle finger represents the direction of the induced current.

 

PROPERTIES OF ELECTROMAGNETIC WAVE

Properties of electromagnetic waves include:

• Electromagnetic waves are propagated through oscillating magnetic and electric waves at right angles to each other.
• Electromagnetic waves are transverse waves. Transverse waves are waves that change or oscillate perpendicularly to the direction of propagation of the wave.
• Electromagnetic waves exhibit the properties of diffraction and interference.
• Electromagnetic waves travel at a speed of 3 x 108 meters per second.

APPLICATIONS OF ELECTROMAGNETISM

Below are examples of the application of electromagnetism:

• Electromagnetism is a fundamental working principle applied in home appliances. Most home electric appliances apply electromagnetism as the basic working principle. These appliances include an electric fan and an electric door bell. In an electric fan, the motor is kept rotating by electromagnetic induction, therefore, rotating the fan. In an electric doorbell, when you press the button, the coil is energized by electromagnetic forces and the bell sounds.
• The principle of electromagnetism is applied in making high-speed trains. Speed trains use powerful electromagnets to generate high speed. Electromagnets on the body of the train are attracted to iron rails, therefore, driving the train toward the direction of the force. Repulsive force can also be used to push the body of a train.
• Electromagnetic radiations are applied in communication systems for data transfer from the source to the receiver. The development of electromagnets was important to the development of long-distance communication instruments like phones. Electromagnetic pulses and the interaction of signals make it possible for phones to operate.
• Electromagnetism is applied in industries in developing medical systems. Electromagnetism plays a vital role in the development of advanced medical equipment like magnetic resonance imaging, and in hyperthermia treatments for cancer. Electromagnetic therapy involves the application of electromagnetic fields to the body. It is an alternative form of medicine. This treatment method is applied to many types of ailments like ulcers, nervous disorders, and diabetes. Many medical types of equipment like x-rays and scanner equipment use the electromagnetism principle to function.

EXAMPLE OF APPLICATION OF ELECTROMAGNETISM

Permanent magnetic speakers mainly used in Radios and TVs are examples of electromagnetic devices. The operation of these devices is based on the electromagnetism principle.

Converting electrical waves to audible sound requires speakers to be designed such that to allow for electromagnetism. A permanent magnet is attached to a metal coil, and when current is passed through the coil, a magnetic field is generated. The magnetic field that is newly formed is repelled by the (other) permanent magnetic field resulting in vibrations. The sound comes from the amplification of these vibrations by cone-like structures.

Summary

We've learned that:

• Electromagnetism is concerned with the study of electromagnetic force.
• Electromagnetic force is a type of physical interaction between charged particles (electrically).
• Electromagnetic force is a combination of magnetic and electrical forces and it occurs between charged particles.
• Electromagnetic induction refers to the principle of generation of voltage or electricity when a conductor is moved through or placed in a magnetic field.
• To propagate electromagnetic waves, you oscillate magnetic and electric waves at right angles to one another.