# Electromagnetic Principles

• ** Electromagnetic field**: A region around a magnetic material or a moving electric charge within which the force of magnetism acts.
• Electromagnet: A soft metal core made into a magnet by the passage of electric current through a coil surrounding it.

# Important Laws and Principles

• Lorentz Force: The force exerted on a charged particle in an electromagnetic field is equal to the electric force plus the magnetic force. Mathematically, F = qE + qvB where ‘q’ is the charge of the particle, ‘E’ is the electric field strength, ‘v’ is the velocity of the particle, and ‘B’ is the magnetic field strength.
• Right-hand rule: A mnemonic for understanding direction of forces in electromagnetic systems. If the thumb points in the direction of the current and the fingers curl in the direction of the magnetic field, the palm points in the direction of the force on a positive charge.
• Ampère’s circuital law: It states that the integral of magnetic field around any closed loop is equal to the product of the permeability and the electric current enclosed in the loop.

# Applications of Electromagnetism

• Electric motors: Useful in various devices like fans, power tools and disk drives which work on the basis of interaction between electric and magnetic fields.
• Transformers: Used to increase or decrease the AC voltages in electric power applications.
• MRI (Magnetic Resonance Imaging): Medical imaging technique used in radiology to form pictures of the anatomy and the physiological processes of the body.

# Measurement Techniques

• Current can be measured using a galvanometer.
• Magnetic field strength can be measured using a fluxmeter.

# Important Conversions

• Tesla to Oersted (Oe): 1 Tesla is approximately equal to 10,000 Oersted. Oersted is the unit of magnetic field strength in the CGS system whereas Tesla is used in the SI system.
• Weber to Maxwells: 1 Weber equals 10^8 Maxwells.

Remember constant practice and understanding of these topics is paramount for a good understanding of Electromagnetism. To do well in your assessments, always use the correct units in your answers and become comfortable with converting between different units.