Electricity and Magnetism

Even if we don't know exactly what they are or how they work, we've all heard of and even used electricity and magnetism, separately or together. We know we need electricity, we generate it for our homes, but how does it work? What rules does electricity follow? We know magnetism exists on earth, but where? Why does it work the way that it does? Also, how do both of these important physics concepts relate to one another? Let's find out.

Definition of Electricity and Magnetism in Physics

In the world of physics, electricity and magnetism tend to go hand in hand. Both play key roles in electromagnetism and electromagnetic fields, and electric charges will not only have a response to electric fields but also to magnetic fields. Electric charges will generate their own magnetic fields when they’re moving through a wire, so in a sense, magnets will also have a response to electric fields sometimes.

To first understand the relationship between electricity and magnetism, we must understand them as separate entities.

Definition of Electricity

Electricity does not have a strict definition, but rather a description.

Electricity can be in one of two forms, either dynamic or static. These forms simply mean if the charged particles that make up electricity are moving or at rest, respectively. Moving charges form a current, and this is the form electricity takes in wires and electric circuits as a whole. On the other hand, static electricity occurs when a shift of electrons happened between two objects that aren’t typically good conductors of electricity, which means the charges of these two objects won’t be balanced.

Definition of Magnetism

Like electricity, magnetism is best introduced as a description rather than a hard definition.

Magnetic fields aren’t visible, and we know they exist because of their interactions with objects capable of interacting with a magnetic field. Examples of objects that can interact with magnetic fields include a small list of metals containing cobalt, nickel, and iron. As well as this, other magnetic fields are capable of interacting with them, including magnetic fields that we know can be generated from current moving through a wire.

Fig. 1. A typical magnet, with a north and south pole.Wikimedia Commons

Difference Between Electricity and Magnetism

We have already established that the relationship between electricity and magnetism is a strong one, but there are still things that set them both apart. For example, electric fields are far more powerful than magnetic fields, in the sense that the forces they exert are more massive compared to the energy required to generate them.

Another key difference between electricity and magnetism is that an electric field can be generated by an electric monopole, which is a single point from which the electric field lines emerge. This isn't possible in magnetism: as magnetic monopoles don't exist, there must always be two poles to a magnetic source, and as such, there are no magnetic fields that have magnetic field lines emerging from a single point.

Effects of Electricity and Magnetism

The effect of an electric charge moving is the induction of a magnetic field. In turn, the effect of a moving magnetic field is the subsequent induction of an electric current.

Fig. 2. An example of a magnetic current inducing an electric field. Wikimedia Commons

Electricity and magnetism have many effects on many things. Notable, however, are the effects on the human body and its health. The human body contains and uses electric currents regularly, in the brain, in the nervous system, and throughout the rest of the body. Electric and magnetic fields running through the body are therefore capable of generating electric current inside your body, possibly causing visual disturbances, as well as muscle movements, as your muscles are activated by electric current. However, for external electric and magnetic fields, this would require a much higher field strength than what is standard in the electric and magnetic fields you may encounter in everyday life, so it isn't a problem you'd expect to ever run into.

Properties of Electricity and Magnetism

We've looked at what electricity and magnetism are capable of causing in terms of effects, what their similarities are, and what their differences are. But what are their actual properties?

The first and most obvious property of magnetism is that it will produce a magnetic attraction or repulsion to objects and materials that are magnetic. Secondly, the poles of magnets will always repel each other if they're the same, and always attract each other if they are opposite. Thirdly, if a magnet is in a state of suspension, with no forces acting on it other than the Earth's magnetic force, it will come to rest in an orientation facing north to south. Finally, if a magnet possesses one pole, it will always have another opposite pole: there are no magnetic monopoles.

The most important property of electricity is that there are electric monopoles: electrons have a negative charge while protons have a positive charge. Like charges will repel each other and opposite charges attract each other. The Earth has no electric field, so a charged object will not have any tendency to a particular direction or orientation if no forces act on it except the electromagnetic field of the Earth.

Example of Electricity and Magnetism in Physics

As you may know, electricity and magnetism are frequently encountered and used in everyday life, especially electricity, as it powers our whole world.

Magnetism

By far the biggest example of magnetism you may know of is the magnetic field covering the entire planet, known as the magnetosphere. The magnetosphere protects us from harmful radiation from out there in deeper space, as well as solar radiation emitted from our Sun.

Fig. 3. The magnetic field of the Earth, with the field emitting from the south pole and entering through the north pole, Wikimedia Commons

Compasses demonstrate magnetism in conjunction with our helpful magnetosphere. The needle in a compass is magnetized, so as long as it is on Earth, the Earth's magnetic field will affect it. The tip of the needle is its north pole, which is why is it attracted to the North Pole: the North Pole is the magnetic south pole.

Electricity

Of course, we know the many uses of electricity and how it powers many of our appliances and machines that we use every day. But how about some of the lesser-known, equally important ways electricity is used? Let's start with electroplating. Electroplating is the process of covering a metal with a layer of oxide that protects it. This is done through the use of an electric current that will dissolve impurities in the metal. See the image below for what this looks like.

Fig. 4. How electroplating works: the spoon is immersed in liquid while a current is flowing between the cathode and anode to coat the metal in the oxide in the liquid, Wikimedia Commons

One of the more fantastical but very real examples of electricity is how some creatures use it as a means of detection. Mostly underwater animals such as sharks will generate their own electric field in an area around their body, and if another creature passes through this field, it would change the field slightly. The shark would know this, as well as where in the field the disturbance occurred, and pounce upon the prey. This is known as electroreception.