Which of the following has zero average value in a plane electromagnetic wave:
Correct answer: D. Both (b) and (c)
- A. Kinetic energy
- B. Magnetic field
- C. Electric field
- D. Both (b) and (c)
Explanation
In an electromagnetic wave, the average value of the electric field or magnetic field is zero, because electromagnetic waves are sinusoids and the average of a sinusoid over 1 period is zero.
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About Alternating Current
Alternating current varies periodically, so phase relationships become essential when current passes through a resistor, capacitor or inductor. The chapter distinguishes resistance from capacitive and inductive reactance, explains phase lead and lag, and connects changing electric and magnetic fields with the production and properties of electromagnetic waves.
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