Magnetic fields

edwinesosa's version from 2015-04-24 10:10


Question Answer
what is a magnetic fielda force field surrounding any magnet or current carrying wire
what is a magnetic fields line of forcethe direction a free north pole would move in the field
what is the motor effectthe force a current carrying wires experiences when placed at a non zero angle to the lines of force of an external magnetic field
what is magnetic flux densitythe force per unit length per unit current on a current carrying conductor at right angles to the magnetic field
unit of magnetic flux densitytesla
how does a electric motor workA coil of insulated wire is connected to a spilt ring commutator which provides the coil with a current. The coil is placed between the poles of a U shaped magnet. the wires at opposite edges of the coil are acted on by magnetic forces in opposite directions. After each half turn of rotation of the coil, the direction of the current is reversed by the split ring commutator.
how is a picture formed on a tv screena beam of electrons is produced by a filament in a vacuum tube and travels towards a fluorescent screen. A magnetic field, produced by coils outside of the tube, directed parallel to the direction of the path of the beams cause a force to be exerted on the beams and make them change direction. this change in direction can be adjusted by changing the size of current producing the magnetic field
why is no work done by a magnetic field on a charged particlethe force is always at right angles to the direction of motion
what is thermionic emmision and 2 examples of usesan electrically heated filament lamp is placed near a positively charged metal anode; the elctrons are attracted towards the anode and pass through a small hole in it. Used in oscillioscopes and cathode ray tv tubes
what happens in a cyclotronit consists of 2 dees in a vacuum chamber. A uniform magnetic field is applied perpendicular to the planes of the dees. A high frequency alternating voltage is applied between the dees. charged particles are directed into one of the dees near the centre of the cyclotron. the magnetic field causes them to travel in a circular path and emerge from the dee, as they emerge from the dee, the alternating voltage is reversed and the same happens in the other dee. (time taken in each dee is independent on speed)
what is a mass spectrometer used forto analyse the type of atoms present in a sample
how does a mass spectrometer workthe atoms in a sample are ionised and directed in a narrow beam at the same velocity through a magnetic field; each ion is deflected in a semi circle by the field onto a detector; the radius of curvature of the path of each ion is different and dependent on the specific charge of each ion as r=mv/BQ; The detector is linked to a computer which is used to show the relative amount of each ion