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23 Nov 2019

On a clear day at a certain location, a 121 V / m vertical electricfield exists near the Earth's surface. At the same place, theEarth's magnetic field has a magnitude of 4.30 10-5 T. Compute theenergy densities of the two fields.
What is the energy density of -:
1) Electric Field in nJ/m3 ?
2) Magnetic Field µJ/m3 ?

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Hubert Koch
Hubert KochLv2
27 Mar 2019

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Related textbook solutions

Physics: Principles with Applications
7th Edition, 2013
Giancoli
ISBN: 9780321625922

Related questions

11) On a clear day at a certain location, a 96 V / m verticalelectric field exists near theEarth's surface. At the same place,the Earth's magnetic field hasa magnitude of 6.20 X10-5T. Compute the energy densities ofthe two fields.

uE = 1nJ/m3
uB = 2µJ/m3

In a certain region of space near Earth's surface, a uniform horizontal magnetic field of magnitude B exists above a level defined to be y=0. Below y=0, the field abruptly becomes zero. A vertical square wire loop has resistivity ρ, mass density ρ(m), diameter d, and side length l. It is initially at rest with its lower horizontal side at y=0 and is then allowed to fall under gravity, with its plane perpendicular to the direction of the magnetic field.

(a) While the loop is perfectly immersed in the magnetic field (as it falls into the zero-field region), determine the magnetic "drag" force that acts on it at the moment when its speed is v.

(b) Assume that the loop achieves a terminal velocity vT before its upper horizontal side exits the field. Determine a formula for vT.

(c) If the loop is made of copper and B=0.80 T, find vT.


A coil of wire is connected to a power supply, and a currentruns in the coil. A single loop of wire is located near the coil,with its axis on the same line as the axis of the coil. The radiusof the loop is 2 cm.




At time t1 the magnetic field at the center of the loop, due to thecoil, is 0.4 T, in the direction shown in the diagram; the currentin the coil is constant.

(a) What is the absolute value of the magnetic flux through theloop at time t1?
Φ mag = T m2
(b) What approximations or assumptions did you make in calculatingyour answer to part (a)?

Check all that apply.

1.The magnitude of the magnetic field due to the coil is uniformover the area of the loop.
2.The magnetic field outside the loop is zero.
3. The magnetic field due to the coil is uniform in direction overthe area of the loop.


(c) What is the direction of the "curly" electric field inside thewire of the loop at time t1? (Remember that at this time thecurrent in the coil is constant.)
E = 0

At a later time t2, the current in the coil begins todecrease.

(d) Now what is the direction of the "curly" electric field in theloop?
counter-clockwise
At time t2 the rate of change of the magnetic field at the centerof the loop, due to the coil, is -0.36 T/s.
(e) At this time, what is the absolute value of the rate of changeof the magnetic flux through the loop?
|dΦmag/dt| = T m2/s
(f) At this time, what is the absolute value of the emf in theloop?
|emf| = V
(g) What is the magnitude of the electric field at location P,which is inside the wire?
|E| = V/m
(h) Now the wire loop is removed. Everything else remains as it wasat time t2; the magnetic field is still changing at the same rate.What is the magnitude of the electric field at location P?
|E| = V/m

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