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1 2 I? A KS OF ELECTRICITY

«o that If c is the deflection when ,r= /

* *7L { / ^b\

j = — _t Z$ / --- •
mv V 2 /

The electric field Is not absolutely constant between the
p'ates, It Is greater dose to the edges than in other parts of
the field, nor it absolutely vanish at all places outside the
plates ; when accuracy is required these points have to be

takers Into account in the calculation of B. A method by which
this may be done was given by the author in the " Phil. Mag.,"
VI, vol. xx, p, 752.

If the particle is simultaneously acted on by magnetic and
electric forces parallel to the axis of #, we may, If the deflec-
tions are small_s superpose the effects due to the magnetic and
electric forces* so that the y, z deflections of the particle
parallel to the axis of j and z respectively are given by the
equation ₌ _e_ _A

z = -£-, B (2)
mir

Thus if we had a stream of charged particles of different

kinds 'I.e. with different values of e[tn) projected from the *
origin with different velocities parallel to the axis of JT, In the
absence of electric and magnetic forces they would all strike a
at x = / at the same point When, however, they are
submitted to the action of electric and magnetic forces they "
get out, and no two particles strike the same point on

the screen unless they are moving at the same speed and also
have the same value of e/m. If we know the deflected
of the particle we can by equations (i) and (2) calcu-
late both the values of v and also the value of ejm ; we have
from these equations



	1 2 I? A KS OF ELECTRICITY «o that If c is the deflection when ,r= / * 7L { / ^b\ j = — _t Z$ / --- • mv V 2 / The electric field Is not absolutely constant between the p'ates, It Is greater dose to the edges than in other parts of the field, nor it absolutely vanish at all places outside the plates ; when accuracy is required these points have to be takers Into account in the calculation of B. A method by which this may be done was given by the author in the " Phil. Mag.," VI, vol. xx, p, 752. If the particle is simultaneously acted on by magnetic and electric forces parallel to the axis of #, we may, If the deflec- tions are small_s superpose the effects due to the magnetic and electric forces so that the y, z deflections of the particle parallel to the axis of j and z respectively are given by the equation ₌ _e_ _A mv z = -£-, B (2) mir Thus if we had a stream of charged particles of different kinds 'I.e. with different values of e[tn) projected from the * origin with different velocities parallel to the axis of JT, In the absence of electric and magnetic forces they would all strike a at x = / at the same point When, however, they are submitted to the action of electric and magnetic forces they " get out, and no two particles strike the same point on the screen unless they are moving at the same speed and also have the same value of e/m. If we know the deflected of the particle we can by equations (i) and (2) calcu- late both the values of v and also the value of ejm ; we have from these equations

	^B