Electric and magnetic fields (EMFs) are invisible areas of energy, often has not conclusively linked cell phone use with any adverse human health problems. Solutions for Chapter E19 Problem 5ASA. Problem Does the magnetic B field have the same relationship to electric charge as the electric E field? Explain. On top of that, ever-industrious humans have produced artificial magnetic fields with power lines, transport systems, electrical appliances, and.
From time to time, a scientific study finds a link between living near high-voltage power lines and illness. Heightened risk of childhood leukemia is the most commonly cited potential health consequence, but whether or not the risk is real has been hard to pin down.
One glaring issue is that scientists have yet to figure out the mechanism by which such weak magnetic fields—which are still in the microtesla range for homes next to power lines—could adversely affect the human body.
Meanwhile, a team of scientists at the Utilities Threshold Initiative Consortium UTIC has been busy working to figure out the threshold at which the human body shows a physiological response to a magnetic field.
According to Alexandre Legros, a medical biophysicist at the Lawson Health Research Institute and Western University in London, Ontario and a UTIC scientist, the smallest magnetic field that has reliably been shown to trigger a response in humans is around 10, to 20, microtesla. When these strong, direction-shifting magnetic fields get directed at a human, small electrical currents begin to pulse through the body.
Above that threshold, the currents can stimulate super-sensitive cells in the retina, known as graded potential neurons, giving the illusion of a white light flickering even when the affected person is in darkness; these visual manifestations are known as magnetophosphenes.
The 10,microtesla threshold is well above the strength of any magnetic field encountered in everyday life.
So in what situations might magnetophosphenes occur? Although modern quantum optics tells us that there also is a semi-classical explanation of the photoelectric effect —the emission of electrons from metallic surfaces subjected to electromagnetic radiation —the photon was historically although not strictly necessarily used to explain certain observations. It is found that increasing the intensity of the incident radiation so long as one remains in the linear regime increases only the number of electrons ejected, and has almost no effect on the energy distribution of their ejection.
What are magnetic fields?
Only the frequency of the radiation is relevant to the energy of the ejected electrons. This quantum picture of the electromagnetic field which treats it as analogous to harmonic oscillators has proven very successful, giving rise to quantum electrodynamicsa quantum field theory describing the interaction of electromagnetic radiation with charged matter.
It also gives rise to quantum opticswhich is different from quantum electrodynamics in that the matter itself is modelled using quantum mechanics rather than quantum field theory. Dynamics[ edit ] In the past, electrically charged objects were thought to produce two different, unrelated types of field associated with their charge property.
Electromagnetic field - Wikipedia
An electric field is produced when the charge is stationary with respect to an observer measuring the properties of the charge, and a magnetic field as well as an electric field is produced when the charge moves, creating an electric current with respect to this observer. Over time, it was realized that the electric and magnetic fields are better thought of as two parts of a greater whole — the electromagnetic field.
Untilwhen the Danish physicist H. InMichael Faradayone of the great thinkers of his time, made the seminal observation that time-varying magnetic fields could induce electric currents and then, inJames Clerk Maxwell published his famous paper A Dynamical Theory of the Electromagnetic Field. What is a magnetic field? A magnetic field is a picture that we use as a tool to describe how the magnetic force is distributed in the space around and within something magnetic.
Explain When we speak of the force due to a magnet or any force for that matter it has to be on something.
What Magnetic Fields Do to Your Brain and Body - The Crux
Strictly speaking a force vector field tells us the magnitude and direction of a force on a small test particle at any point. With the electric force the small test particle we use is the electron. It turns out that there is no equivalent particle for the magnetic force. The term magnetic monopole is given to such a particle.
As far as we know, magnetic monopoles don't exist in nature and all magnetic field sources are dipolar in nature.
Most of us have some familiarity with everyday magnetic objects and recognize that there can be forces between them. We understand that magnets have two poles and that depending on the orientation of two magnets there can be attraction opposite poles or repulsion similar poles. We recognize that there is some region extending around a magnet where this happens. The magnetic field describes this region.
There are two different ways that a magnetic field is typically illustrated: In reality, the magnetic field extends through 3D space, though for gaining a basic understanding of magnetic fields and solving many problems a 2D description is sufficient. The magnetic field is described mathematically as a vector field. This vector field can be plotted directly as a set of many vectors drawn on a grid. Each vector points in the direction that a compass would point and has length dependent on the strength of the magnetic force.
Explain compasses A compass is nothing more than a tiny magnet suspended such that it can freely rotate in response to a magnetic field. Like all magnets, a compass needle has a north pole and a south pole that are attracted and repelled by the poles of other magnets.