Comparing Electric and Magnetic Quantities

Study Notes

Comparing Electric and Magnetic Quantities

Permittivity and Permeability are analogous quantities describing the ability of material to store electric and magnetic energy respectively.
- Permittivity (ε) is measured in Farads per meter (F/m) and is defined as the ratio of electric displacement field (D) to electric field (E).
- Permeability (μ) is measured in Henries per meter (H/m) and is defined as the ratio of magnetic flux density (B) to magnetic field strength (H).
- Both are expressed as a product of relative permittivity (εr) or permeability (μr) and the permittivity (εo) or permeability (μo) of free space.
Charges and Poles are analogous concepts representing sources of electric and magnetic fields respectively.
- Electric charges can exist separately as positive and negative, while magnetic poles always come in pairs, a North and a South pole.
- Both like charges/poles repel and unlike charges/poles attract.
Electric and Magnetic fields are created around electric charges and magnetic poles respectively and can be described by Gauss's Law and Coulomb's Law for electric fields and Ampère's Law for magnetic fields.
- Electric field (E) is measured in Newtons per Coulomb (N/C) or Volts per meter (V/m).
- Magnetic field strength (H) is measured in Amperes per meter (A/m).
- Electric flux density (D) is measured in Coulombs per square meter (C/m2) and is proportional to E.
- Magnetic flux density (B) is measured in Tesla (T) and is proportional to H.
Electric flux (ΦE) and magnetic flux (ΦH) represent the amount of electric or magnetic field lines passing through an area.
- Electric flux is measured in Volt-meters (V-m) and magnetic flux is measured in Ampere-meters (A-m).
- Electric flux is also measured in Coulombs (C) and is proportional to the electric field strength.
- Magnetic flux is also measured in Webers (Wb) and is proportional to the magnetic field strength.
Electric and Magnetic forces act on charges and magnetic materials respectively.
- Electric force (FE) is calculated using Coulomb's Law or the electric field strength.
- Magnetic force (FB) is calculated using the magnetic field strength and the velocity of a moving charge or the current flowing through a conductor.
- Both forces are measured in Newtons (N).
Electromotive Force (EMF) and Magnetomotive Force (MMF) are driving forces for electric and magnetic circuits respectively.
- EMF is generated by varying magnetic flux and is measured in Volts (V).
- MMF is generated by the flow of current in a coil and is measured in Ampere-Turns (A-t).
Resistance (R) and Reluctance (Rm) are analogous concepts representing opposition to the flow of electric current and magnetic flux respectively.
- Resistance is measured in Ohms (Ω) and Reluctance is measured in Ampere-Turns per Weber (A-t/Wb).
Capacitance (C) and Inductance (L) are analogies representing the ability of materials to store electric and magnetic energy respectively.
- Capacitance is measured in Farads (F) and Inductance is measured in Henries (H).