Electric Fields and Magnetism

 Electrically charged objects produce electric fields around them. These fields produce electric flux with directions pointing outward or inward depending on the charge polarity of the charged object as shown below:

The positively charged objects produce electric flux lines pointing outward while the negatively charged objects produce electric flux lines pointing inward as illustrated above.

The stronger the Electric Field the stronger the interaction between charged objects. Similar charges repulse and dissimilar charges attract as illustrated below:

The intensity of Electrical Fields in space is measured in VOLTS per METER. That is two opposite charge objects with potential difference of 1 VOLT at distance of 1 METER will produce an ELECTRICAL FIELD of 1 VOLT per METER. The greater the charges on the objects the greater the number of ELECTRIC FLUX lines in space and the greater the interaction forces between them. These lines are the imaginary lines of forces that exist between charged objects. Electric Flux is measured as ELECTRIC FLUX DENSITY and is in Coulombs per Square meter or electrons per unit area. One Coulomb C equals to 6,280,000,000,000,000,000 electrons or 6.28 X (10^18) electrons.

The Electric Flux Density is inversely proportional to the square of distance between charged objects. For example if the distance between charged objects is increased by 2 times (doubled) the Electric Flux Density will decrease by 4 times. As the distance between two charged objects increases the number of flux lines per unit area is reduced accordingly. This is like saying if you drive away from the radio station then the radio signal received by your radio fades away. The difference between the radio signal and the charged objects is that the charged objects keep their polarity fixed while the radio wave changes polarity or intensity with time.

Positive charge means an absence of negative electrons, and negative charge means that electrons do exist. The larger the number of electrons contained in the object the more negative the object is and the smaller the number of electrons in the object the more positive the object is. It is all relative.

The attraction (or repulsion) force that exists between the charges (positive and/or negative) mentioned above depends on the charge magnitude of each object, the distance between them, and the medium. This relation is described in the following Columb's Law:

F = (Q1 . Q2) / (4 . π . Є. R² )

Where:

F is the force in Newtons (N)

Q1 and Q2 are the charges in Columbs (C)

Є is the Permittivity of the Medium in C²/N.m² or Farads per meter (F/m)

And R is the distance between these two objects in meters (m)

 

Bottom Line

 Magnetic fields can be thought of as imaginary Flux lines, more lines mean stronger Magnetic field. A useful definition is a Weber, that is the quantity of magnetism. For small magnets the unit Maxwell is used instead of Weber:

1 Weber = 100,000,000 Maxwell or 10 to the power 8 (10^8) Maxwell.

Magnets or fields come in different sizes and shapes. For that a more accurate definition would be the number of  Webers (or number of Maxwells) per unit area:

Tesla = 1 Weber per meter square (m^2) or: 1 Tesla = 1 Weber / m^2

For smaller magnets the Gause is used for measurement, as compared to Tesla:

1 Gause = 1 Tesla / cm ^ 2

Remember that 1 Tesla (T) = 10,000 Gauses (G), or:

1 T = 10^4 G

When the magnet is activated by DC electricity the Ampere-Turn (At) is used. The Gilbert (Gb) is a smaller unit of Ampere-Turn:

1 Ampere-Turn = 1.257 Gilbert

Or:

1 At = 1.257 Gb

 

 

 

 

 

 

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  By: Firas Faham