Explore BrainMass

Faraday's Law

Faraday’s law of induction predicts how a magnetic field will interact with an electric circuit to produce the electromotive force. This law is the fundamental principle of transformers, inductors, generators and solenoids which allow them to operate.

Electromagnetic induction was first discovered by Michael Faraday and Joseph Henry independently in 1831. Faraday published the results of his findings first.¹ He explained electromagnetic induction using a concept he called "line of force". Scientist at the time rejected his theoretical ideas. This was due to the lack of mathematical formulation.

Faraday’s law of induction makes use of magnetic flux through a hypothetical surface whose boundary condition is a wire loop. The magnetic flux is defined by a surface integral. The Maxwell-Faraday equation is:

∇ x E = -∂B/ ∂t

The fields are usually functions of position r and time t. The Maxwell-Faraday equation is one of the four Maxwell’s equations, and therefore plays a fundamental role in the theory of classical electromagnetism.



1. Ulaby, Fawwaz (2007). Fundamentals of applied electromagnetics. (5th ed.). Pearson:Prentice Hall. p. 255. ISBN 0-13-241326-4 

Dissolution rate of silver-20% gold allow, assuming an average density

A silver-20% gold alloy sample (1 cm diameter and 0.2 cm height) is subjected to a selective silver dissolution in 0.1 M HNO3 at current density of 1 mA/cm^2. How long will it take until the total amount of silver is dissolved? Assume the average density of 8 g/ cm^3 for the alloy sample.

Transformer in Circuit

The transformer in the following circuit (see attached file Figure 4.10) has a turns ratio of 10. A sinusoidal voltage of 10 V rms is applied at terminals 11'. What is I_2? (See attached file for full problem description)

Generations (Calculate Maximum EMF in Coil)

A 95 turn square wire coil of area 0.040 m2 rotates about a vertical axis at 1730 rpm, as indicated in Figure P20.30 {attached}. The horizontal component of the Earth's magnetic field at the location of the loop is 2.0 10-5 T. Calculate the maximum emf induced in the coil by the Earth's field. (answer in V)