|a)||Define the term "magnetic flux density".|
|b)||An electron is moving at 107ms-1 at 90° to a magnetic field. The electron follows a circular path of radius 5×10-6m. Calculate the magnitude of the flux density.|
A beam of alpha particles passes undeflected through a region of space in which there are a magnetic field (of flux density 5×10-2T) and an electric field (of field strength 750Vm-1) at 90° to each other. Calculate the speed of the particles.
|The charge to mass ratio of an electron is 1·76×1011Ckg-1. Calculate the time period of the circular motion of an electron in a magnetic field of flux density 0·1T.|
A proton enters a uniform magnetic field of flux density, B = 0·1T with a velocity of 104ms-1 at 60° to the flux lines. It follows a helical path.
|a)||the time taken to complete one revolution of the helical path|
|b)||the distance moved parallel to the flux lines during this time|
|c)||the kinetic energy possessed by the proton when it is in the magnetic field (mass of a proton = 1·67×10-27kg).|
|A very long straight wire lies along the z axis and carries a current, I which flows in the positive z direction in a vacuum (see diagram below).|
|Two flux densities BA and BB are measured at points A (x = 0, y = 10cm, z = 0) and B (x = 0, y = 20cm, z = 0)|
|a)||In which direction do BA and BB act?|
|b)||If I = 1·5A, calculate the magnitude of BA.|
|c)||What value of current would produce a flux density at point B equal to the value you have just calculated for BA?|
Find the magnitudes and directions of the flux densities BC and BD at the points C and D
C has co-ordinates x = 4cm, y = 4cm, z = 0cm
D has co-ordinates x = 4cm, y = 4cm, z = 10cm
A piece of wire is 8cm long and is placed at an angle of 30° to a magnetic field of flux density 0·5T. Calculate the magnitude of the force acting on the wire when a current of 500mA flows through it.
Name the rule used to predict the direction of the force on the wire.
|a)||Explain why a moving coil galvanometer must have control springs (or something equivalent to control springs).|
|b)||How is a moving coil galvanometer made to have a high current sensitivity?|
|c)||A moving coil galvanometer could be made without a soft iron cylinder. What would be the main disadvantage of a meter without a soft iron cylinder?|
Two straight wires are parallel to each other and 5cm apart. Wire A-B has a current of I1 = 5A flowing through it and wire C-D has a current of I2 = 20A flowing through it (see diagram below).What is the magnitude and direction of the electro-magnetic force acting on wire A-B?