When E and B are the amplitudes of the electric and magnetic fields in an electromagnetic wave in vacuum, the total average energy density in the wave is
A.
.B.
.C.
D.
.E.
.Answer: B
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If a negative charge is placed inside a hollow isolated conductor that is originally neutral and the charge does not touch that conductor at any time:
a. both the inner and outer surfaces will become negative. b. both the inner and outer surfaces will remain neutral. c. the outside surface of the conductor will become positively charged. d. the inside surface of the conductor will become positively charged.
Does all electromagnetic radiation travel at the speed of light?
What will be an ideal response?
If air were a better conductor than it is, nighttimes on Earth would be
A) considerably colder. B) considerably warmer. C) not appreciably different in temperature.
Which of the following best represents the energy transformations in a coal-fired electric power plant?
A) chemical ? thermal ? kinetic ? electromagnetic B) radiant ? kinetic ? electromagnetic ? thermal C) electromagnetic ? thermal ? kinetic D) gravitational ? kinetic ? electromagnetic E) chemical ? kinetic ? thermal ? electromagnetic