A charged particle moves along a circle understand the action of uniform magnetic field and electric field then the region of space may have
Answers
Answer:
Magnetic force can cause a charged particle to move in a circular or spiral path. Cosmic rays are energetic charged particles in outer space, some of which approach the Earth. They can be forced into spiral paths by the Earth’s magnetic field. Protons in giant accelerators are kept in a circular path by magnetic force. The bubble chamber photograph in [link] shows charged particles moving in such curved paths. The curved paths of charged particles in magnetic fields are the basis of a number of phenomena and can even be used analytically, such as in a mass spectrometer.
oscillating electrons generate the microwaves sent into the oven.
Tokamaks such as the one shown in the figure are being studied with the goal of economical production of energy by nuclear fusion. Magnetic fields in the doughnut-shaped device contain and direct the reactive charged particles. (credit: David Mellis, Flickr)
Figure a shows a tokamak in a lab. Figure b is a diagram of a tokamak. A current-carrying wire wraps around a donut-shaped vacuum chamber. Inside the chamber is plasma. The magnetic field has a toroidal and poloidal shape inside the chamber.
Mass spectrometers have a variety of designs, and many use magnetic fields to measure mass. The curvature of a charged particle’s path in the field is related to its mass and is measured to obtain mass information. (See More Applications of Magnetism.) Historically, such techniques were employed in the first direct observations of electron charge and mass. Today, mass spectrometers (sometimes coupled with gas chromatographs) are used to determine the make-up and sequencing of large biological molecules.
Section Summary
Magnetic force can supply centripetal force and cause a charged particle to move in a circular path of radius
r=\frac{\text{mv}}{\text{qB}},
where v is the component of the velocity perpendicular to B for a charged particle with mass m and charge q.
Conceptual Questions
How can the motion of a charged particle be used to distinguish between a magnetic and an electric field?
High-velocity charged particles can damage biological cells and are a component of radiation exposure in a variety of locations ranging from research facilities to natural background. Describe how you could use a magnetic field to shield yourself.
If a cosmic ray proton approaches the Earth from outer space along a line toward the center of the Earth that lies in the plane of the equator, in what direction will it be deflected by the Earth’s magnetic field? What about an electron? A neutron?
What are the signs of the charges on the particles in [link]?
Diagram showing magnetic field lines into the page. Charges are moving from the bottom to the top of the diagram and thus perpendicular to the field lines. Charge a curves to the left. Charge b moves in a straight line from bottom to top. Charge c curves to the right.
Which of the particles in [link] has the greatest velocity, assuming they have identical charges and masses?
Diagram showing magnetic field lines out of the page. Charge a curves clockwise with a large radius as it moves from the bottom to the top of the diagram. Charge b curves clockwise with a much smaller radius as it moves from lower middle to upper middle of the diagram.
Which of the particles in [link] has the greatest mass, assuming all have identical charges and velocities?
While operating, a high-precision TV monitor is placed on its side during maintenance. The image on the monitor changes color and blurs slightly. Discuss the possible relation of these effects to the Earth’s magnetic field.
Problems & Exercises
If you need additional support for these problems, see More Applications of Magnetism.
A cosmic ray electron moves at 7\text{.}\text{50}×{\text{10}}^{6}\phantom{\rule{0.25em}{0ex}}\text{m/s} perpendicular to the Earth’s magnetic field at an altitude where field strength is 1\text{.}\text{00}×{\text{10}}^{-5}\phantom{\rule{0.25em}{0ex}}\phantom{\rule{0.25em}{0ex}}T. What is the radius of the circular path the electron follows?
4.27 m
A proton moves at 7\text{.}\text{50}×{\text{10}}^{7}\phantom{\rule{0.25em}{0ex}}\text{m/s} perpendicular to a magnetic field. The field causes the proton to travel in a circular path of radius 0.800 m. What is the field strength?
(a) Viewers of Star Trek hear of an antimatter drive on the Starship Enterprise. One possibility for such a futuristic energy source is to store antimatter charged particles in a vacuum chamber, circulating in a magnetic field, and then extract them as needed. Antimatter annihilates with normal matter, producing pure energy. What strength magnetic field is needed to hold antiprotons, moving at 5\text{.}\text{00}×{\text{10}}^{7}\phantom{\rule{0.25em}{0ex}}\text{m/s} in a circular path 2.00 m in radius? Antiprotons have the same mass as protons but the opposite (negative) charge. (b) Is this field strength obtainable with today’s technology or is it a futuristic possibility?