Magnetic Fields

• Magnetic field is a region in which a force acts on a wire or other magnet
• Field lines go from the north to the south pole of a magnet. The closer together the lines, the stronger the field is.
• Magnetic Field is induced when a current flows through a wire.
• The right-hand rule is used to work out the direction of the magnetic field in a current-carrying wire.
• Fleming's Left-hand rule is used to work out the direction of the current, external magnetic field and force on the wire.
• The Magnetic Flux density is the force on one metre of wire carrying a current of one amp at right angles to the magnetic field.
• Magnetic Flux density is measured in Tesla. One tesla equals one newton per one amp metre. $1T =$$1 N/ 1 Am$
• $F=$$BIL$gives the maximum force the wire could experience. When the wire is 90 degrees to a magnetic field, force is proportional to the current, lenght and the flux density.
• $F =$$BQv$is the equation to calculate the force that acts on a charged particle moving in a magnetic field
• The radius of the circular path by a charged particle in a magnetic field is calculated by $r =$$mv/BQ$
• The radius of the curvature of a charged particle, moving in a magnetic field, will increase if the mass or velocity increases. r is proportional to mv.
• The radius of the curvature of a charged particle, moving in a magnetic field, will decrease if the flux density (strength of magnetic field) or the charge of the particle in the field increases. r is inversely proportional to BQ
• The frequency of rotation of a charged particle , moving in a magnetic field is given by $f =$$BQ/ 2(pi)m$
• Magnetic Flux Density is the strength of a magnetic field.
• The total Magnetic Flux passing through an area perpendicular to a magnetic field is given by $magnetic flux linkage =$$BA$
• Faraday's Law states that Induced e.m.f is directly proportional to the rate of change in flux linkage.
• Lenz's law states that the direction of the induced emf is opposite to the direction of the current.
• Lenz's law states that the induced emf is akways in such direction as to oppose the change that caused it.
• Transformers are devices that change the size of the voltage for an alternating current.