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# Electricity and Magnetism ## Want to get better grades?

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Electricity and Magnetism
• Astrophysics • Atoms and Radioactivity • Circular Motion and Gravitation • Conservation of Energy and Momentum • Dynamics • Electric Charge Field and Potential • Electricity • Electricity and Magnetism • Electromagnetism • Electrostatics • Energy Physics • Engineering Physics • Fields in Physics • Fluids • Force • Fundamentals of Physics • Further Mechanics and Thermal Physics • Geometrical and Physical Optics • Kinematics Physics • Linear Momentum • Magnetism • Magnetism and Electromagnetic Induction • Measurements • Mechanics and Materials • Medical Physics • Modern Physics • Nuclear Physics • Oscillations • Particle Model of Matter • Physical Quantities and Units • Physics of Motion • Radiation • Rotational Dynamics • Scientific Method Physics • Space Physics • Thermodynamics • Torque and Rotational Motion • Translational Dynamics • Turning Points in Physics • Waves Physics • Work Energy and Power 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 described as encompassing all the phenomena that occur as a result of electrical charges.

Electric fields are areas in which an electric force can be felt.

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.

How good a material is at conducting or insulating electricity depends on whether or not the atoms that make up the material have a lot of free electrons. This is known as the valence of an atom, and the more so-called valence electrons, the better the material will conduct electricity.

### Definition of Magnetism

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

Magnetism can be described as encompassing all the phenomena that occur as a result of the magnetization of permanent and induced magnets and of charges that are in motion.

Magnet fields are the areas in which magnetic force can be felt.

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

When an electric field is generated from a magnetic field, or vice versa, this combination is responsible for a so-called electromagnetic field. This field sometimes transmits waves, which we call electromagnetic waves. These waves are responsible for a lot of things we see in everyday life, as radio waves, microwaves, visible light waves, X-rays, and gamma rays all fall under electromagnetic waves.

## 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. 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. 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. 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.

## Electricity and Magnetism - Key takeaways

• Electricity and magnetism have many similarities and differences.
• Both play key roles in electromagnetic fields and electromagnetic waves, like radio waves, microwaves, visible light, X-rays, and gamma rays.
• However, electric fields are usually much stronger than magnetic fields, and there are electric monopoles while there are no magnetic monopoles.
• Electricity and magnetism both affect each other and one can always induce the other.
• Electricity is used in the human body to send messages through neurons.
• Properties of magnetism:
• Like magnetic poles repel each other and opposite magnetic poles attract each other.
• The Earth has a magnetic field that influences all magnets.
• There are no magnetic monopoles.
• Properties of electricity:
• Like electric charges repel each other and opposite electric charges attract each other.
• There are electric monopoles, e.g. electrons and protons.
• An example of electricity in physics is electroplating.
• An example of magnetism in physics is the Earth's magnetosphere.

An example of electricity and magnetism is the electromagnetic field. Both an electric field and magnetic field oscillate simultaneously generating electromagnetic forces that have a multitude of uses.

Electricity and magnetism are similar things, electricity is the flow and presence of charges which can induce a magnetic field, and magnetism in turn can move charges to generate an electric current.

Electricity and magnetism are similar, but not the same. A difference in them is present in electromagnetic fields, where they both oscillate, but perpendicular to one another.

Electricity and magnetism are both important as they both exist commonly on the planet. We use electricity to power our homes, and magnetic forces covering the Earth protect us from harmful radiation in space.

Electricity produces magnetism by moving charges. By running a current through a coil of wire, a magnetic field will be induced.

## Final Electricity and Magnetism Quiz

Question

Which of the following statements are correct?

Like charges repel each other.

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Question

Which of the following is correct?

An electron flow will only occur within a closed circuit.

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Question

Which of the following particles have a non-zero electric charge?

Protons.

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Question

How many electrons, protons, and neutrons are present in an atom of copper?

29 electrons, 29 protons, 34 neutrons.

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Which of the following materials are good conductors of electricity?

All metals.

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Why are metals good conductors of electricity?

They have valence electrons.

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Which of the following is the correct unit for the current?

amperes.

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Question

What is the definition of electric current?

An electric current is the amount of charge passing through a wire per unit of time.

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In an electric circuit, what is the direction of a conventional current?

From the positive terminal to the negative terminal of the battery.

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What is the definition of a conventional current?

The conventional current is the flow of positive charge in a circuit, or minus the flow of negative charge.

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Question

What will happen to the number of charges passing through a point of a wire in one minute if the current in the wire is increased?

It would increase.

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Question

If the amplitude of the magnetic field is changing with time, then an electric field will be induced.

True.

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Question

In a changing magnetic field, a current can be induced even if there is no conductor in the field.

False.

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Question

In a changing magnetic field, the electric field will be induced even if there is no loop wire.

True.

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Question

You can generate an electric field around an area by altering the magnetic flux in that area.

True.

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Question

True.

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Question

The induced voltage in a coil with four loops will be double that of a coil with one loop.

False.

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Question

In an electromagnetic wave, only the electric field will be changing with time.

False.

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Question

The induced electric field lines in a varying magnetic field should be represented by a closed loop.

True.

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Question

Whenever there are electric forces, there must be a magnetic field.

False.

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Question

If there is no conductor in the varying magnetic field, then neither voltage nor current can be induced.

True.

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Question

Heating a bar magnet would increase its magnetic field.

False.

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Question

The Earth's magnetic field has experienced countless polarity reversals over geological time.

True.

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The magnetic force is stronger when the distance is smaller.

True.

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Question

Not every magnet is surrounded by a magnetic field.

False.

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Question

True.

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Question

What's the definition of an electric field?

The electric field is defined as the space where electrical forces can act on a unit electric charge.

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Question

The electric field is a scalar quantity.

False.

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Question

The magnitude of the electric field is directly proportional to the magnitude of the charge.

True.

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Question

The magnitude of the electric field is directly proportional to the square of the distance.

False.

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The direction of the electric field generated by a positive charge is outward while by a negative charge it is towards the charge.

True.

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Question

The electric field lines extend from positive charge to infinity and from infinity to negative charge.

True.

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Electric field lines may cross each other.

False.

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Question

The intensity of the electric field lines is proportional to the magnitude of the electric field.

True.

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Electric field lines extend symmetrically in three dimensions.

True.

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Question

If the electrical potential energy between two equal charges quadruples, describe the change in the distance between the particles.

The distance was quartered

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If the electrical potential energy between two equal charges doubles, describe the change in the distance between the particles.

The distance was halved.

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If the electrical potential energy between two charges doubles and the distance is constant, describe the change in the multiplication of the charges.

The multiplication of the charges doubles.

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Question

Charges that repel each other have positive energy, while charges that attract each other have negative energy.

True.

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Question

True or false, there is no SI unit for electrical potential energy.

False.

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Question

True or false, when work is done on a positive test charge to move it from one location to another, potential energy increases.

True.

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Question

What type of relationship do voltage and current have for ohmic conductors?

A directly proportional relationship.

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Question

What physical condition is required for a metal conductor to exhibit Ohm's law?

A constant temperature.

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Question

What is the slope of an I-V graph for an ohmic conductor?

1/R

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Question

What type of conductor is a copper wire?

Ohmic.

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Question

All resistors are ohmic. Is this statement true or false?

False.

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Question

Is a transistor an ohmic or non-ohmic conductor?

Non-ohmic.

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Question

Why can less current flow per unit voltage as the current in a filament bulb increases?

An increase in current increases the temperature, which causes an increase in resistance and so less current can flow per unit voltage.

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Question

As the temperature of a thermistor increases, does its resistance increase or decrease?

It decreases.

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Question

For a filament bulb, is the resistance higher for lower currents or higher currents?

Higher currents.

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