72 W. A. Norton on Molecular Physics. 
supposed to move, the theoretical result is in nig phi accordance 
with the facts as experimentally established by Farada 
In the foregoing we have supposed the wire, carmen to the 
magnet, to be moved parallel to itself to various points of the 
magnetic field; but Faraday has shown that a current may also 
be induced in the wire, by bending it into a curve and causing 
it to revolve around the magnet, after one end has been brought 
into contact with the equatorial bis of the magnet, and the 
other with a wire or rod leading 
from the pole, as shown in fig. TL. 
“A copper ring was fixed round and 
in z gecioiges she the equatorial part, 
e, made to bear by 
se pees against this ring, a 
oO against a-ring on the axis.” “The direction of the current 
changed with the direction of revolution. Corresponding cur- 
rents were also obtained by rotating the magnet in the opposite 
directions, the wire remaining fixed. To explain these currents 
upon the principles now developed, we must first observe that 
the impulsive force of the magnet will impart a transverse polar- 
ization to the molecules of the Ste oe let a motion of rev- 
ieee tHe gs This pclaiastett should be ‘attended with a 
direction of the length of the wire. There shot: then, be an 
inequality in this disturbance at the point of contact, e. This 
inequality should originate a current that would pass around 
the circuit. Let v denote the velocity answering to the acne 
impulse, and v’ the velocity of revolution of the molecule at e. 
bist the effect due to the polarizing force at the end, e, of the 
may be represented by m (v-+v’)®, and that induced in the 
contiguous particles of the copper ring by mv?. The difference 
is mv’(2v-+-v'), which represents the electro-motive ei — the 
current. If the wire were made to revolve around an unmag- 
netized bar, the originating force of the current would be mv'?. 
would exceed this nearly 
in the ratio of 2v to o “A hile a velocity of revolution of 
> wire would re be vo a A ei lop a sensible cur- 
if the bar were ) 
ve expression 
poet Shamil ec ake ae tinting: Saat 
— a ee tea ore, Mins sled velocity, v 
ea 
motive fore, vi, mv 0-0), Sd 
Rost ce wie oe 
