Bachelor of Applied Science
Electromechanical Energy Conversion
Applications of Faraday’s Law of Electromagnetic Induction
Dr. Adel El Gammal
Done by:
Shae Mark-59234
24/09/2018
1. INTRODUCTION
The purpose of this report was to gain an in-depth understanding of the theoretical principles that
governs Faraday’s law of induction. The law of induction states that an induced electromotive
force is equal to the rate of change of magnetic flux through the circuit. The objective was to
analyze the principles of Faraday’s law and discuss how it related to electrical guitars, apnea
monitors, induction stoves and electromagnetic guns.
2. THEORETICAL BACKGROUND
2.1 Guitar
Faraday’s law of induction states that the electromotive force induced in a coil is dependent on
the number (N) of loops in the coil times the rate of change of the magnetic flux (𝜙) in the coil
[1].
𝐸𝑀𝐹 = −𝑁
𝑑ϕ
𝑑𝑡
3. ANALYSIS AND DISCUSSION
3.1 Electric Guitar
The electric guitar was designed to produce audible sound by converting the string’s vibration to
an electrical signal. The component responsible for the conversion is called the pickup, the
pickup consists of numerous copper coil, circuit wires, and magnets. Each string that runs along
the guitar is attached to the magnets of the pickup. When the strings are stroked they resonate
causing a change in flux going through the coil; when the magnetized string moves close to the
coil it exerts a force on the charges in the coil. As a result, the coil emits a fluctuating voltage
function as the coil vibrates up and down; the induced voltage is directly proportional the
number of turnings and the rate of change of flux with respect to time. The emitted signal can be
sent to an amplifier to make the signal louder.
Figure 1. Diagram of an electronic guitar
3.2 Apnea Monitor
An apnea monitor detects the cessation of breathing in persons who are at risk of respiratory
failure. The apnea machine is connected to the patients via pneumatic abdominal sensors,
thermistors, proximal airway pressure sensors, and carbon dioxide sensors [2]. The sensor is
designed with a coil of wire that is wrapped all the way around the patient’s chest, and an
induced alternating current through it. As the patient’s chest expands and contracts the field area
changes, causing an induced electromotive force through a nearby pick up coil. If the patient’s
breathing ceases there will be a change in the induced current and the apnea monitor will sound
[3]. The apnea monitor should be frequently calibrated and maintained to avoid alarm failure or
misinterpreted data.
Figure 2. Apnea monitor attached to infant
3.3 Induction Stove
The concept of an induction stove is cooking using the principle of electrical induction. The pot
or pan used for cooking must be made of a ferromagnetic metal such as cast iron or stainless
steel. The component responsible for heating the cooking utensil is known as an induction hob.
Under the ceramic hob lies a coil of copper wire, when a cooking utensil is placed onto the
surface an alternating current is generated. This results in a changing magnetic field and induces
a magnetic flux. When the direction of the magnetic field is changed it causes eddy currents to
run through the material of the pot. As the eddy currents travel through the pot, it causes the
molecules to resist the current resulting in heat energy.
Figure 3. Induction Stove
3.4 The Electromagnetic Gun
The electromagnetic gun is an energy conversion device made up of two parallel metal rails that
is electrically connected to an armature. When current is applied a magnetic field is created, it
interacts with the armature and the electrons flow from the negative pole of the power supply
through the projectile and back down the positive pole. The current direction in the rails are in
opposite direction, the net magnetic field between them causes an induce magnetic force that
accelerates the particle along the rails.
Figure 4. Electromagnetic gun
4. REFERENCES
[1] B. Hopkin, R. Cain and J. Lollar, Getting A Bigger Sound, 2nd ed. Nicasio, CA: Windworld,
2003.
[2] T. Hirst, Electric guitar construction. Anaheim Hills, Calif.: Centerstream, 2003.
[3] "Faraday’s Law of Induction: Lenz’s Law – College Physics", Opentextbc.ca, 2018. [Online].
Available: https://opentextbc.ca/physicstestbook2/chapter/faradays-law-of-induction-lenzs-law/.
[Accessed: Sep. 25, 2018].
[4] Who.int, 2018. [Online]. Available:
http://www.who.int/medical_devices/innovation/apnea_monitor.pdf. [Accessed: Sep. 25, 2018].
[5] "How Does Induction Cooking Work? | CDA Appliances", Cda.eu, 2018. [Online]. Available:
https://www.cda.eu/hobs/how-does-induction-cooking-work. [Accessed: Sep. 25, 2018].