Wikibooks: OCR A-Level Physics/Fields, Particles and Frontiers of Physics/Magnetic Fields

• Format: Book
• Language: English
• Subjects: North Pole; South Pole; The Thumb; Thumb; Will Point; South pole
• Online Access: https://en.wikibooks.org/wiki/OCR_A-Level_Physics/Fields,_Particles_and_Frontiers_of_Physics/Magnetic_Fields

In order to answer the relevant questions in the exam it is necessary to have an understanding of magnetic fields and associated concepts such as magnetic flux and magnetic flux density. = Magnetic field lines = Like electric fields magnetic fields can be represented by field lines. The direction of the lines shows the direction of the magnetic field while the density of the lines shows the magnetic field strength (known as the magnetic flux density ). The magnetic field lines for a current carrying wire appear as concentric circles around the wire with the direction of the field being shown by the right hand grip rule. According to this rule if you point the thumb of your right hand in the direction of conventional current in the wire the direction in which your fingers grip around the thumb is the direction of the magnetic field. The magnetic field inside a solenoid (coil) is uniform inside the coil with the field directed from its south pole to its north pole. There are also curved field lines outside the coil which are directed from the north to the south pole. For any magnetic field lines start from the north pole to the south pole.Lines are smooth curves which never touch nor cross.Strength is indicated by the distance between the lines closer the lines means stronger field = Fleming s Left Hand Rule= The relationship between the direction of magnetic field the direction of the current in a current carrying wire and the force experienced by the wire is shown by Fleming s left hand rule. This states that if you hold the thumb first finger and second finger of your left hand at right angles to each other the thumb will point in the direction of the force experienced by the wire if the first finger follows the direction of the magnetic field from North to South and the second finger shows the direction of conventional current (+ to ) inside the conductor. = Magnitude of magnetic force = Using Fleming s left hand rule on its own is rarely sufficient in physics it is also important to know the magnitude of the ...