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.

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. $\frac{1}{2}$.

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.

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?

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?

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?

Which quantities remain constant when alternating currents are generated?

Which of the following would not increase the emf produced by a generator? A. rotating the generator coil faster, B. increasing the strength of the generator magnets, C. increasing the number of turns of wire in the coil, D. reducing the cross-sectional area of the coil.

A 256-turn coil with a cross-sectional area of 0.0025 $\mathrm{m}^{2}$ is placed in a uniform external magnetic field of strength 0.25 T so that the plane of the coil is perpendicular to the field. The coil is pulled steadily out of the field in 0.75 s. Find the average induced emf during this interval.

A television picture tube requires a high potential difference, which a step-up transformer provides in older models. The transformer has 12 turns in its primary and 2550 turns in its secondary. If 120 V is applied across the primary, what is the output emf?

What four factors affect the magnitude of the induced emf in a coil of wire?