Why is a longer antenna needed to produce a low-frequency radio wave than to produce a high-frequency radio wave?

Why does electromagnetic radiation obey the inverse-square law?

Electric guitar strings are made of ferromagnetic materials that can be magnetized. The strings lie closely over and perpendicular to a coil of wire. Inside the coil are permanent magnets that magnetize the segments of the strings overhead. Using this arrangement, explain how the vibrations of a plucked string produce an electrical signal at the same frequency as the vibration of the string.

If you have a fixed magnetic field and a length of wire, how can you increase the induced emf across the ends of the wire?

Suppose a fixed distance separates the centers of two circular loops. What relative orientation of the loops will give the maximum mutual inductance? What orientation will give the minimum mutual inductance?

Where is the energy of an electromagnetic wave stored? Describe how this energy can be used.

By what factor do you multiply the maximum emf to calculate the rms emf for an alternating current? F. 2, G. $\sqrt{2}$, H. $\frac{1}{\sqrt{2}}$, J. $\frac{1}{2}$.

What is the average value of current over one cycle of an ac signal? Why, then, is a resistor heated by an ac current?

How does the behavior of low-energy electromagnetic radiation differ from that of high-energy electromagnetic radiation?

How are electric and magnetic fields oriented to each other in an electromagnetic wave?

Voltmeters and ammeters that measure ac quantities are calibrated to measure the rms values of emf and current, respectively. Why would this be preferred to measuring the maximum emf or current?

In a Ground Fault Interrupter, would the difference in current across an outlet be measured in terms of the rms value of current or the actual current at a given moment? Explain your answer.

How does the power dissipated in a resistor by an alternating current relate to the power dissipated by a direct current that has potential difference and current values that are equal to the maximum values of the alternating current?

Which quantities remain constant when alternating currents are generated?