ACT Science : How to find conflicting viewpoints in physics
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Example Question #1 : How To Find Conflicting Viewpoints In Physics
Sound waves travel through a medium by mechanically disturbing the particles of that medium. As particles in the medium are displaced by the sound wave, they in turn act upon neighboring particles. In this fashion, the wave travels through the medium through a parallel series of disturbed particles. Like in other forms of motion, the rate at which the sound wave travels can be measured by dividing the distance over which the wave travels by the time required for it to do so.
Study 1
A group of students hypothesizes that the velocity of sound is dependent upon the density of the medium through which it passes. They propose that with more matter in a given space, each particle needs to travel a shorter distance to disturb the adjacent particles. Using two microphones and a high speed recording device, the students measured the delay from the first microphone to the second. They chose a variety of media, shown in Table 1, and measured the velocity of sound through each using their two-microphone setup. The results are found in Table 1.
Study 2
The students wanted to test their hypothesis by using the same medium at different densities. To do this, they heated pure water to various temperatures and repeated the procedure described in Study 1. Their results can be found in Table 2.
If the students' hypotheses were correct, what might be a worthwhile question for them to study next?
What is the velocity of sound in water over 100°C?
Does the length of the sample used affect the velocity of sound through a substance?
What other properties of matter affect velocity of sound through a substance?
Does density affect the velocity of sound in substances other than those tested in Study 1?
What other properties of matter affect velocity of sound through a substance?
If the velocity of sound through a substance is directly dependent upon the density of the substance, then that would mean increasing density should always result in increasing velocity. Because this is not the case (see "lead" in Table 1 and the increasing velocities as density decreases in Table 2), there must be another factor or multiple factors affecting the velocity of sound as it travels through a substance.
The students' correct hypotheses would account for the remaining answer choices, so these would require no further investigation.
Example Question #2 : How To Find Conflicting Viewpoints In Physics
Sound waves travel through a medium by mechanically disturbing the particles of that medium. As particles in the medium are displaced by the sound wave, they in turn act upon neighboring particles. In this fashion, the wave travels through the medium through a parallel series of disturbed particles. Like in other forms of motion, the rate at which the sound wave travels can be measured by dividing the distance over which the wave travels by the time required for it to do so.
Study 1
A group of students hypothesizes that the velocity of sound is dependent upon the density of the medium through which it passes. They propose that with more matter in a given space, each particle needs to travel a shorter distance to disturb the adjacent particles. Using two microphones and a high speed recording device, the students measured the delay from the first microphone to the second. They chose a variety of media, shown in Table 1, and measured the velocity of sound through each using their two-microphone setup. The results are found in Table 1.
Study 2
The students wanted to test their hypothesis by using the same medium at different densities. To do this, they heated pure water to various temperatures and repeated the procedure described in Study 1. Their results can be found in Table 2.
Suppose a second group of students hypothesizes that the velocity of sound is inversely dependent upon the density of the substance through which the sound travels. Which study would best support their hypothesis and why?
Study 1, because velocity decreases as density decreases
Study 2, because velocity decreases as density increases
Study 2, because velocity increases as density increases
Study 1, because velocity decreases as density increases
Study 2, because velocity decreases as density increases
In order for velocity to be inversely dependent upon density, one must increase as the other decreases. This is most consistent with the results of Study 2.
Example Question #1 : How To Find Conflicting Viewpoints In Physics
The graph below depicts the position of three different cars over a 15-second time interval.
Two students have conflicting views on determining which, if any, cars are accelerating. Which is the best method of determining which car is accelerating?
Determining which cars are traveling at a constant speed in the same direction
Observing which cars cross position zero
Forming a position vs. velocity graph, and noting which cars have increasing velocities
Noting on the graph any car that has a slope greater or less than zero, but not equal to zero
Forming a position vs. velocity graph, and noting which cars have increasing velocities
A position vs. velocity graph would help show if any cars have increasing or decreasing velocities, which, by definition, is acceleration or deacceleration, respectively. A car traveling at a constant speed is not accelerating. Where cars cross position zero is not relevant for the question stem. Any car with a slope not equal to zero tells us that the car is moving or has a speed, it does not, however, tell us whether the car is accelerating or not. Visually, an accelerating car would have a position that changes in the same direction by greater and greater amounts over the same timer interval, as in the case of car 3 over time 4s to 9s.
Example Question #1261 : Act Science
Magnets and electric charges show certain similarities. For example, both magnets and electric charges can exert a force on their surroundings. This force, when produced by a magnet, is called a magnetic field. When it is produced by an electric charge, the force is called an electric field. It has been observed that the strength of both magnetic fields and electric fields is inversely proportional to the square of the distance between a magnet or an electric charge and the objects that they affect.
Below, three scientists debate the relationship between electricity and magnetism.
Scientist 1:
Electricity and magnetism are two different phenomena. Materials such as iron, cobalt, and nickel contain magnetic domains: tiny regions of magnetism, each with two poles. Normally, the domains have a random orientation and are not aligned, so the magnetism of some domains cancels out that of other domains; however, in magnets, domains line up in the same direction, creating the two poles of the magnet and causing magnetic behavior.
In contrast, electricity is a moving electric charge which is caused by the flow of electrons through a material. Electrons flow through a material from a region of higher potential (more negative charge) to a region of lower potential (more positive charge). We can measure this flow of electrons as current, which refers to the amount of charge transferred over a period of time.
Scientist 2:
Electricity and magnetism are similar phenomena; however, one cannot be reduced to the other. Electricity involves two types of charges: positive and negative charge. Though electricity can occur in a moving form (in the form of current, or an electric charge moving through a wire), it can also occur in a static form. Static electricity involves no moving charge. Instead, objects can have a net excess of positive charge or a net excess of negative charge—because of having lost or gained electrons, respectively. When two static positive electric charges or two static negative electric charges are brought close together, they repel each other. However, when a positive and a negative static charge are brought together, they attract each other.
Similarly, all magnets have two poles. Magnetic poles that are alike repel each other, while dissimilar magnetic poles attract each other. Magnets and static electric charges are alike in that they both show attraction and repulsion in similar circumstances. However, while isolated static electric charges occur in nature, there are no single, isolated magnetic poles. All magnets have two poles, which cannot be dissociated from each other.
Scientist 3:
Electricity and magnetism are two aspects of the same phenomenon. A moving flow of electrons creates a magnetic field around it. Thus, wherever an electric current exists, a magnetic field will also exist. The magnetic field created by an electric current is perpendicular to the electric current's direction of flow.
Additionally, a magnetic field can induce an electric current. This can happen when a wire is moved across a magnetic field, or when a magnetic field is moved near a conductive wire. Because magnetic fields can produce electric fields and electric fields can produce magnetic fields, we can understand electricity and magnetism as parts of one phenomenon: electromagnetism.
In an experiment, an iron bar that showed no magnetism was heated and allowed to cool while aligned North-South with the Earth's magnetic field. After it cooled, the iron bar was found to be magnetic. Scientist 1 would most likely explain this result by saying which of the following?
The experiment caused the magnetic domains of the bar to move out of alignment with each other.
The experiment induced an electric current in the bar, causing the bar to become magnetic.
Interference occurred between the electric field of the bar and the magnetic field of the Earth, causing the bar to become magnetic.
The experiment caused the two magnetic poles of the bar to move so that they were aligned with the Earth's magnetic field.
The experiment allowed the magnetic domains of the bar to line up, causing the bar to become magnetic.
The experiment allowed the magnetic domains of the bar to line up, causing the bar to become magnetic.
Scientist 1 states that magnetism occurs when the magnetic domains in a material align. Since the iron bar initially showed no magnetism, we can assume that its magnetic domains were initially oriented randomly, and that it had no magnetic poles. Since the iron bar became magnetic after it was heated and cooled, the heating and cooling process likely reoriented the magnetic domains in the iron so that they became more aligned, creating two magnetic poles.
Example Question #1262 : Act Science
Magnets and electric charges show certain similarities. For example, both magnets and electric charges can exert a force on their surroundings. This force, when produced by a magnet, is called a magnetic field. When it is produced by an electric charge, the force is called an electric field. It has been observed that the strength of both magnetic fields and electric fields is inversely proportional to the square of the distance between a magnet or an electric charge and the objects that they affect.
Below, three scientists debate the relationship between electricity and magnetism.
Scientist 1:
Electricity and magnetism are two different phenomena. Materials such as iron, cobalt, and nickel contain magnetic domains: tiny regions of magnetism, each with two poles. Normally, the domains have a random orientation and are not aligned, so the magnetism of some domains cancels out that of other domains; however, in magnets, domains line up in the same direction, creating the two poles of the magnet and causing magnetic behavior.
In contrast, electricity is a moving electric charge which is caused by the flow of electrons through a material. Electrons flow through a material from a region of higher potential (more negative charge) to a region of lower potential (more positive charge). We can measure this flow of electrons as current, which refers to the amount of charge transferred over a period of time.
Scientist 2:
Electricity and magnetism are similar phenomena; however, one cannot be reduced to the other. Electricity involves two types of charges: positive and negative charge. Though electricity can occur in a moving form (in the form of current, or an electric charge moving through a wire), it can also occur in a static form. Static electricity involves no moving charge. Instead, objects can have a net excess of positive charge or a net excess of negative charge—because of having lost or gained electrons, respectively. When two static positive electric charges or two static negative electric charges are brought close together, they repel each other. However, when a positive and a negative static charge are brought together, they attract each other.
Similarly, all magnets have two poles. Magnetic poles that are alike repel each other, while dissimilar magnetic poles attract each other. Magnets and static electric charges are alike in that they both show attraction and repulsion in similar circumstances. However, while isolated static electric charges occur in nature, there are no single, isolated magnetic poles. All magnets have two poles, which cannot be dissociated from each other.
Scientist 3:
Electricity and magnetism are two aspects of the same phenomenon. A moving flow of electrons creates a magnetic field around it. Thus, wherever an electric current exists, a magnetic field will also exist. The magnetic field created by an electric current is perpendicular to the electric current's direction of flow.
Additionally, a magnetic field can induce an electric current. This can happen when a wire is moved across a magnetic field, or when a magnetic field is moved near a conductive wire. Because magnetic fields can produce electric fields and electric fields can produce magnetic fields, we can understand electricity and magnetism as parts of one phenomenon: electromagnetism.
When two wires carrying electric currents are placed near each other, it is found that each of the wires exerts a slight attraction on the other. Scientist 3 would most likely explain this by saying which of the following?
Each of the two wires produces a magnetic field parallel to it, and the magnetic fields attract each other.
Each of the two wires produces an electric field perpendicular to it, and the electric fields repel each other.
Static charges on each of the two wires become attracted to each other when the wires are placed close together.
Each of the two wires produces a magnetic field perpendicular to it, and the magnetic fields exert an attraction on each other.
Each of the two wires produces a magnetic field perpendicular to it, and the magnetic fields exert an attraction on each other.
In the first paragraph of her explanation, Scientist 3 states that an electric current can induce a magnetic field around it. So, when there are two wires carrying electric currents, she will assume that both of the wires produce a magnetic field. Since the two wires are attracted to each other, the magnetic fields likely also attract each other. Finally, Scientist 3 also states that the magnetic field produced by an electric current exists perpendicular to the current's direction of flow. So, the magnetic fields are oriented perpendicular to the wires that produce them.
Example Question #2 : How To Find Conflicting Viewpoints In Physics
Magnets and electric charges show certain similarities. For example, both magnets and electric charges can exert a force on their surroundings. This force, when produced by a magnet, is called a magnetic field. When it is produced by an electric charge, the force is called an electric field. It has been observed that the strength of both magnetic fields and electric fields is inversely proportional to the square of the distance between a magnet or an electric charge and the objects that they affect.
Below, three scientists debate the relationship between electricity and magnetism.
Scientist 1:
Electricity and magnetism are two different phenomena. Materials such as iron, cobalt, and nickel contain magnetic domains: tiny regions of magnetism, each with two poles. Normally, the domains have a random orientation and are not aligned, so the magnetism of some domains cancels out that of other domains; however, in magnets, domains line up in the same direction, creating the two poles of the magnet and causing magnetic behavior.
In contrast, electricity is a moving electric charge which is caused by the flow of electrons through a material. Electrons flow through a material from a region of higher potential (more negative charge) to a region of lower potential (more positive charge). We can measure this flow of electrons as current, which refers to the amount of charge transferred over a period of time.
Scientist 2:
Electricity and magnetism are similar phenomena; however, one cannot be reduced to the other. Electricity involves two types of charges: positive and negative charge. Though electricity can occur in a moving form (in the form of current, or an electric charge moving through a wire), it can also occur in a static form. Static electricity involves no moving charge. Instead, objects can have a net excess of positive charge or a net excess of negative charge—because of having lost or gained electrons, respectively. When two static positive electric charges or two static negative electric charges are brought close together, they repel each other. However, when a positive and a negative static charge are brought together, they attract each other.
Similarly, all magnets have two poles. Magnetic poles that are alike repel each other, while dissimilar magnetic poles attract each other. Magnets and static electric charges are alike in that they both show attraction and repulsion in similar circumstances. However, while isolated static electric charges occur in nature, there are no single, isolated magnetic poles. All magnets have two poles, which cannot be dissociated from each other.
Scientist 3:
Electricity and magnetism are two aspects of the same phenomenon. A moving flow of electrons creates a magnetic field around it. Thus, wherever an electric current exists, a magnetic field will also exist. The magnetic field created by an electric current is perpendicular to the electric current's direction of flow.
Additionally, a magnetic field can induce an electric current. This can happen when a wire is moved across a magnetic field, or when a magnetic field is moved near a conductive wire. Because magnetic fields can produce electric fields and electric fields can produce magnetic fields, we can understand electricity and magnetism as parts of one phenomenon: electromagnetism.
In a compass, a needle spins to align North-South, following the Earth's magnetic field. Suppose that a compass is placed near wire through which an electric current flows, and it is observed that the needle of the compass no longer aligns to North-South. How would this affect the arguments of Scientist 2 and Scientist 3?
It would strengthen Scientist 2's argument, and it would weaken Scientist 3's argument.
It would strengthen Scientist 2's argument, and it would strengthen Scientist 3's argument.
It would weaken Scientist 2's argument, and it would strengthen Scientist 3's argument.
It would weaken Scientist 2's argument, and it would weaken Scientist 3's argument.
It would have no effect on Scientist 2's argument, and it would strengthen Scientist 3's argument.
It would have no effect on Scientist 2's argument, and it would strengthen Scientist 3's argument.
Here, since the (magnetic) compass no longer aligns to North-South when it is near the wire, this implies that there is some kind of magnetic field near the wire which is interfering with the compass. This supports what Scientist 3 says in the first paragraph of her explanation: that an electric current can induce a magnetic field around it.
Scientist 2, however, makes no mention of this kind of electromagnetic induction in his explanation; however, he also does not say that it is not possible. His explanation is mostly about how magnetic poles are similar to and different from static electric charges. So, his argument is not affected by the observation that an electric current induces a magnetic field.
Example Question #1263 : Act Science
Magnets and electric charges show certain similarities. For example, both magnets and electric charges can exert a force on their surroundings. This force, when produced by a magnet, is called a magnetic field. When it is produced by an electric charge, the force is called an electric field. It has been observed that the strength of both magnetic fields and electric fields is inversely proportional to the square of the distance between a magnet or an electric charge and the objects that they affect.
Below, three scientists debate the relationship between electricity and magnetism.
Scientist 1:
Electricity and magnetism are two different phenomena. Materials such as iron, cobalt, and nickel contain magnetic domains: tiny regions of magnetism, each with two poles. Normally, the domains have a random orientation and are not aligned, so the magnetism of some domains cancels out that of other domains; however, in magnets, domains line up in the same direction, creating the two poles of the magnet and causing magnetic behavior.
In contrast, electricity is a moving electric charge which is caused by the flow of electrons through a material. Electrons flow through a material from a region of higher potential (more negative charge) to a region of lower potential (more positive charge). We can measure this flow of electrons as current, which refers to the amount of charge transferred over a period of time.
Scientist 2:
Electricity and magnetism are similar phenomena; however, one cannot be reduced to the other. Electricity involves two types of charges: positive and negative charge. Though electricity can occur in a moving form (in the form of current, or an electric charge moving through a wire), it can also occur in a static form. Static electricity involves no moving charge. Instead, objects can have a net excess of positive charge or a net excess of negative charge—because of having lost or gained electrons, respectively. When two static positive electric charges or two static negative electric charges are brought close together, they repel each other. However, when a positive and a negative static charge are brought together, they attract each other.
Similarly, all magnets have two poles. Magnetic poles that are alike repel each other, while dissimilar magnetic poles attract each other. Magnets and static electric charges are alike in that they both show attraction and repulsion in similar circumstances. However, while isolated static electric charges occur in nature, there are no single, isolated magnetic poles. All magnets have two poles, which cannot be dissociated from each other.
Scientist 3:
Electricity and magnetism are two aspects of the same phenomenon. A moving flow of electrons creates a magnetic field around it. Thus, wherever an electric current exists, a magnetic field will also exist. The magnetic field created by an electric current is perpendicular to the electric current's direction of flow.
Additionally, a magnetic field can induce an electric current. This can happen when a wire is moved across a magnetic field, or when a magnetic field is moved near a conductive wire. Because magnetic fields can produce electric fields and electric fields can produce magnetic fields, we can understand electricity and magnetism as parts of one phenomenon: electromagnetism.
Given that all of the following are true, which of the following, if found, provides the strongest evidence against Scientist 1's hypothesis?
The magnetic domains of a material are partially created by the spin and electric charge of the electrons within the material.
A magnetic field affects the position of iron filings. However, an electric field has no effect on the position of iron filings.
Running an electric current through a magnet does not cause a change in the strength of the magnetic field around the magnet.
When one pole of a magnet is placed near a wire carrying a current, the magnet is attracted to the wire. When the other pole of the magnet is placed in the same position, the magnet is repelled.
When one pole of a magnet is placed near a wire carrying a current, the magnet is attracted to the wire. When the other pole of the magnet is placed in the same position, the magnet is repelled.
Scientist 1 states that electricity and magnetism are completely separate phenomena; however, if a wire carrying an electric current exerts an attractive force on one pole of a magnet and a repulsive force on the other pole of the magnet, there must be an interaction between the electricity flowing through the wire and the magnet. Specifically, it seems like the electricity flowing through the wire is creating its own magnetic field, which attracts one pole of the magnet and repels the other pole.
Example Question #3 : How To Find Conflicting Viewpoints In Physics
Magnets and electric charges show certain similarities. For example, both magnets and electric charges can exert a force on their surroundings. This force, when produced by a magnet, is called a magnetic field. When it is produced by an electric charge, the force is called an electric field. It has been observed that the strength of both magnetic fields and electric fields is inversely proportional to the square of the distance between a magnet or an electric charge and the objects that they affect.
Below, three scientists debate the relationship between electricity and magnetism.
Scientist 1:
Electricity and magnetism are two different phenomena. Materials such as iron, cobalt, and nickel contain magnetic domains: tiny regions of magnetism, each with two poles. Normally, the domains have a random orientation and are not aligned, so the magnetism of some domains cancels out that of other domains; however, in magnets, domains line up in the same direction, creating the two poles of the magnet and causing magnetic behavior.
In contrast, electricity is a moving electric charge which is caused by the flow of electrons through a material. Electrons flow through a material from a region of higher potential (more negative charge) to a region of lower potential (more positive charge). We can measure this flow of electrons as current, which refers to the amount of charge transferred over a period of time.
Scientist 2:
Electricity and magnetism are similar phenomena; however, one cannot be reduced to the other. Electricity involves two types of charges: positive and negative charge. Though electricity can occur in a moving form (in the form of current, or an electric charge moving through a wire), it can also occur in a static form. Static electricity involves no moving charge. Instead, objects can have a net excess of positive charge or a net excess of negative charge—because of having lost or gained electrons, respectively. When two static positive electric charges or two static negative electric charges are brought close together, they repel each other. However, when a positive and a negative static charge are brought together, they attract each other.
Similarly, all magnets have two poles. Magnetic poles that are alike repel each other, while dissimilar magnetic poles attract each other. Magnets and static electric charges are alike in that they both show attraction and repulsion in similar circumstances. However, while isolated static electric charges occur in nature, there are no single, isolated magnetic poles. All magnets have two poles, which cannot be dissociated from each other.
Scientist 3:
Electricity and magnetism are two aspects of the same phenomenon. A moving flow of electrons creates a magnetic field around it. Thus, wherever an electric current exists, a magnetic field will also exist. The magnetic field created by an electric current is perpendicular to the electric current's direction of flow.
Additionally, a magnetic field can induce an electric current. This can happen when a wire is moved across a magnetic field, or when a magnetic field is moved near a conductive wire. Because magnetic fields can produce electric fields and electric fields can produce magnetic fields, we can understand electricity and magnetism as parts of one phenomenon: electromagnetism.
According to Scientist 2, which of the following would be an example of a static electric charge?
A balloon that has been rubbed against hair so that it has picked up excess electrons
A ring of a conductive material, such copper, that has not lost or gained electrons
A conductive material, such as copper, that is placed in an magnetic field
A bar magnet placed in an electric field
A wire that carries charge from the negative to the positive terminal of a battery
A balloon that has been rubbed against hair so that it has picked up excess electrons
Scientist 2 states that static electric charges occur when an object has a net excess of positive or negative charge. According to Scientist 2, static electric charges also don't involve a moving charge. So, one example of a static electric charge is a balloon that has picked up excess electrons: it has an excess of negative charge, but the charge is not moving.
Example Question #1264 : Act Science
Magnets and electric charges show certain similarities. For example, both magnets and electric charges can exert a force on their surroundings. This force, when produced by a magnet, is called a magnetic field. When it is produced by an electric charge, the force is called an electric field. It has been observed that the strength of both magnetic fields and electric fields is inversely proportional to the square of the distance between a magnet or an electric charge and the objects that they affect.
Below, three scientists debate the relationship between electricity and magnetism.
Scientist 1:
Electricity and magnetism are two different phenomena. Materials such as iron, cobalt, and nickel contain magnetic domains: tiny regions of magnetism, each with two poles. Normally, the domains have a random orientation and are not aligned, so the magnetism of some domains cancels out that of other domains; however, in magnets, domains line up in the same direction, creating the two poles of the magnet and causing magnetic behavior.
In contrast, electricity is a moving electric charge which is caused by the flow of electrons through a material. Electrons flow through a material from a region of higher potential (more negative charge) to a region of lower potential (more positive charge). We can measure this flow of electrons as current, which refers to the amount of charge transferred over a period of time.
Scientist 2:
Electricity and magnetism are similar phenomena; however, one cannot be reduced to the other. Electricity involves two types of charges: positive and negative charge. Though electricity can occur in a moving form (in the form of current, or an electric charge moving through a wire), it can also occur in a static form. Static electricity involves no moving charge. Instead, objects can have a net excess of positive charge or a net excess of negative charge—because of having lost or gained electrons, respectively. When two static positive electric charges or two static negative electric charges are brought close together, they repel each other. However, when a positive and a negative static charge are brought together, they attract each other.
Similarly, all magnets have two poles. Magnetic poles that are alike repel each other, while dissimilar magnetic poles attract each other. Magnets and static electric charges are alike in that they both show attraction and repulsion in similar circumstances. However, while isolated static electric charges occur in nature, there are no single, isolated magnetic poles. All magnets have two poles, which cannot be dissociated from each other.
Scientist 3:
Electricity and magnetism are two aspects of the same phenomenon. A moving flow of electrons creates a magnetic field around it. Thus, wherever an electric current exists, a magnetic field will also exist. The magnetic field created by an electric current is perpendicular to the electric current's direction of flow.
Additionally, a magnetic field can induce an electric current. This can happen when a wire is moved across a magnetic field, or when a magnetic field is moved near a conductive wire. Because magnetic fields can produce electric fields and electric fields can produce magnetic fields, we can understand electricity and magnetism as parts of one phenomenon: electromagnetism.
When a wire coil is rotated between the poles of a magnet, an electric current is produced in the wire. How does this observation affect the argument of Scientist 3?
It supports Scientist 3's argument because it shows that a magnetic field can induce an electric current.
It supports Scientist 3's argument because it shows that an electric current can produce a magnetic field.
It weakens Scientist 3's argument because it shows that an electric current can produce a magnetic field.
It weakens Scientist 3's argument because it shows that a magnetic field can induce an electric current.
It supports Scientist 3's argument because it shows that a magnetic field can induce an electric current.
In the second paragraph of her explanation, Scientist 3 states that a magnetic field can induce an electric current. Specifically, she says that moving a wire across a magnetic field can induce a current in the wire. This idea is supported by the observation that rotating (moving) a wire coil between the poles of a magnet (in a magnetic field) induces an electric current.
Example Question #4 : How To Find Conflicting Viewpoints In Physics
Magnets and electric charges show certain similarities. For example, both magnets and electric charges can exert a force on their surroundings. This force, when produced by a magnet, is called a magnetic field. When it is produced by an electric charge, the force is called an electric field. It has been observed that the strength of both magnetic fields and electric fields is inversely proportional to the square of the distance between a magnet or an electric charge and the objects that they affect.
Below, three scientists debate the relationship between electricity and magnetism.
Scientist 1:
Electricity and magnetism are two different phenomena. Materials such as iron, cobalt, and nickel contain magnetic domains: tiny regions of magnetism, each with two poles. Normally, the domains have a random orientation and are not aligned, so the magnetism of some domains cancels out that of other domains; however, in magnets, domains line up in the same direction, creating the two poles of the magnet and causing magnetic behavior.
In contrast, electricity is a moving electric charge which is caused by the flow of electrons through a material. Electrons flow through a material from a region of higher potential (more negative charge) to a region of lower potential (more positive charge). We can measure this flow of electrons as current, which refers to the amount of charge transferred over a period of time.
Scientist 2:
Electricity and magnetism are similar phenomena; however, one cannot be reduced to the other. Electricity involves two types of charges: positive and negative charge. Though electricity can occur in a moving form (in the form of current, or an electric charge moving through a wire), it can also occur in a static form. Static electricity involves no moving charge. Instead, objects can have a net excess of positive charge or a net excess of negative charge—because of having lost or gained electrons, respectively. When two static positive electric charges or two static negative electric charges are brought close together, they repel each other. However, when a positive and a negative static charge are brought together, they attract each other.
Similarly, all magnets have two poles. Magnetic poles that are alike repel each other, while dissimilar magnetic poles attract each other. Magnets and static electric charges are alike in that they both show attraction and repulsion in similar circumstances. However, while isolated static electric charges occur in nature, there are no single, isolated magnetic poles. All magnets have two poles, which cannot be dissociated from each other.
Scientist 3:
Electricity and magnetism are two aspects of the same phenomenon. A moving flow of electrons creates a magnetic field around it. Thus, wherever an electric current exists, a magnetic field will also exist. The magnetic field created by an electric current is perpendicular to the electric current's direction of flow.
Additionally, a magnetic field can induce an electric current. This can happen when a wire is moved across a magnetic field, or when a magnetic field is moved near a conductive wire. Because magnetic fields can produce electric fields and electric fields can produce magnetic fields, we can understand electricity and magnetism as parts of one phenomenon: electromagnetism.
Which of the following would be an example of electricity according to Scientist 2, but not according to Scientist 1?
A positively-charged object is attracted to a negatively-charged object and receives excess electrons from it.
Current flows along a wire between a negatively-charged object and an positively charged-object.
A wire conducts electrons from the negative terminal of a battery to the positive terminal.
Two negatively-charged objects repel each other.
Two negatively-charged objects repel each other.
According to Scientist 2, electricity can take on two forms: static electricity and current electricity. Scientist 2 states that while current electricity consists of a moving electric charge, static electricity involves no moving charge. Scientist 2 also states that static electricity can cause two objects to repel or attract each other. In contrast, Scientist 1 defines electricity as a moving charge—he states that electricity must involve the flow of electrons.
So, a situation where there is no flow of electrons—where two objects repel each other due to static electricity—would be seen as an example of electricity by Scientist 2, but not by Scientist 1.
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