Magnetic Field of a Long Wire: At a point 10 m away from a long straight thin wire, the magnetic field due to the wire is 0.10 mT. What current flows through the wire? (?0 = 4? × 10-7 T ? m/.A
Fill in the blank(s) with the appropriate word(s).
5.0 kA
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If you walk toward a mirror at a certain speed, the relative speed between you and your image is
A) half your speed. B) your speed. C) twice your speed. D) none of the above
A wire of perimeter P and cross-sectional area A emerges from a die at a temperature T (above ambient temperature) and with a velocity U. Determine the temperature distribution along the wire in the steady state if the exposed length downstream from the die is quite long. State clearly and try to justify all assumptions.
GIVEN
• A wire emerging from a die at a temperature (T) above ambient
• Wire perimeter = P
• Cross-sectional area = A
• Wire emerges at a temperature T above ambient
• Wire velocity = U
FIND
• The temperature distribution along the wire in the steady state if the exposed length downstream from the die is quite long. State clearly and try to justify all assumptions
ASSUMPTIONS
• Ambient temperature is constant at T?
• Heat transfer coefficient between the wire and the air is uniform and constant at hc
• The material properties of the wire are constant
? Thermal conductivity = k
? Thermal diffusivity = ?
• Axial conduction only
• Wire temperature is uniform at a cross section (negligible internal thermal resistance)
SKETCH
A 100-m long wire carrying a current of 4.0 A will be accompanied by a magnetic field of what strength at a distance of 0.040 m from the wire? (magnetic permeability in empty space µ0 = 4p × 10^-7 T×m/A)
a. zero c. 2.0 × 10^-5 T b. 1.6 × 10^-5 T d. 4.0 × 10^-5 T