Learning from mistakes: the case of clinical electrophysiology: a perspective on evidence-based rhythmology

The magnitude and direction of a magnetic field created by a steady current can be calculated using the Biot-Savart law.
Consider a mobile phone battery bank as a source of steady current, which flows through the wire connected between the two. What is the magnitude of the magnetic field created by this current at a field point P?
To estimate the magnitude of the total magnetic field, we first consider a small current element of length dl, at a distance r from the field point. Now the following...

Ampere's law states that for any closed looped path, the line integral of the magnetic field along the path equals the vacuum permeability times the current enclosed in the loop. If the fingers of the right hand curl along the direction of the integration path, the current in the direction of the thumb is considered positive. The current opposite to the thumb direction is considered negative.
Specific steps need to be considered while calculating the symmetric magnetic field distribution using...

An emf is induced when the magnetic field in a coil is changed by pushing a bar magnet into or out of the coil. emfs of opposite signs are produced by motion in opposite directions, and the directions of emfs are also reversed by reversing poles. The same results are produced if the coil is moved rather than the magnet—it is the relative motion that is important. The faster the motion, the greater the emf. Additionally, there is no emf when the magnet is stationary relative to the coil.
A...

Faraday's law state that the induced emf is the negative change in the magnetic flux per unit of time. Any change in the magnetic field or change in the orientation of the area of the coil with respect to the magnetic field induces a voltage (emf). The magnetic flux measures the number of magnetic field lines through a given surface area. Magnetic flux is estimated from the integral of the dot product of the magnetic field vector and the area vector. The negative sign describes the direction in...

The direction in which the induced emf drives the current around a wire loop can be found through the negative sign. However, it is usually easier to determine this direction with Lenz's law, named in honor of its discoverer, Heinrich Lenz (1804–1865). Lenz's law states that the direction of the induced emf drives the current around a wire loop always to oppose the change in magnetic flux that causes the emf.
If a bar magnet is moved toward a coil such that the magnetic flux through the coil...

The total current density in magnetized material is the sum of the free and bound current densities. The free current arises due to the motion of free electrons within the material, while the bound current arises due to the alignment of magnetic dipole moments.
The differential form of Ampere's law in vacuum states that the curl of the magnetic field equals the permeability times the current density. In a magnetized material, the law is modified to incorporate the free and bound current...