Chapter 11, Problem 14TE

Joseph Henry's wife tearfully sacrificed part of her wedding gown for silk to cover the wires of electromagnets. What was the purpose of the silk covering?

Solution

To determine:

The purpose of silk coverings in the development of Joseph Henry's electromagnet.

Answer:

The purpose of silk coverings in the development of Joseph Henry's electromagnet was to insulate individual turns of the coil thereby increasing the power of the electromagnet.

Explanation:

The electromagnet uses the principle which states that a current carrying conductor has a perpendicular magnetic field associated with it. As the magnitude of current increases, so does the magnitude of the magnetic field associated with it. Thus, when there are multiple turns in a coil of wire, the magnetic field that is produced by the electromagnet multiplies that many times.As the individual turns of wire in a coil need to conduct current in the same direction, it is necessary that the turns of wire need to be insulated from each other. Hence, silk which is an insulator at normal conditions, is used to cover the wire and thereby create a layer between successive turns of the coil of wire and help increase the power of an electromagnet.

Conclusion:

Therefore, the purpose of silk coverings in the development of Joseph Henry's electromagnet was to insulate individual turns of the coil thereby increasing the power of the electromagnet.