Chapter 29: Q. 23 (page 831)
The value of the line integral of around the closed path in FIGURE EX29.23 is . What are the direction (in or out of the page) and magnitude of ?
Short Answer
The current and it is points into the paper.
Chapter 29: Q. 23 (page 831)
The value of the line integral of around the closed path in FIGURE EX29.23 is . What are the direction (in or out of the page) and magnitude of ?
The current and it is points into the paper.
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Get started for freea. In FIGURE P29.76, a long, straight, current-carrying wire of linear mass density is suspended by threads. A magnetic field perpendicular to the wire exerts a horizontal force that deflects the wire to an equilibrium angle . Find an expression for the strength and direction of the magnetic field .
b. What deflects a 55 g/m wire to a 12° angle when the current is 10 A?
What are the magnetic fields at points a to c in FIG URE EX29.12? Give your answers as vectors.
A proton in a cyclotron gains of kinetic energy per revolution, where is the potential between the dees. Although the energy gain comes in small pulses, the proton makes so many revolutions that it is reasonable to model the energy as increasing at the constant rate , where is the period of the cyclotron motion. This is power input because it is a rate of increase of energy.
a. Find an expression for , the radius of a proton's orbit in a cyclotron, in terms of . Assume that at .
Hint:Start by finding an expression for the proton's kinetic energy in terms of .
b. A relatively small cyclotron is in diameter, uses a magnetic field, and has a potential difference between the dees. What is the power input to a proton, in ?
c. How long does it take a proton to spiral from the center out to the edge?
FIGURE EX29.37 is a cross-section through three long wires with a linear mass density . They each carry equal currents in the directions shown. The lower two wires are apart and are attached to a table. What current I will allow the upper wire to “float” so as to form an equilateral triangle with the lower wires?
The toroid of is a coil of wire wrapped around a doughnut-shaped ring (a torus). Toroidal magnetic fields are used to confine fusion plasmas.
a. From symmetry, what must be the shape of the magnetic field in this toroid? Explain.
b. Consider a toroid with N closely spaced turns carrying current I. Use Ampère’s law to find an expression for the magnetic field strength at a point inside the torus at distance r from the axis.
c. Is a toroidal magnetic field a uniform field? Explain.
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