A pendulum, suspended at the origin, consists of two non- conducting massless ro
ID: 1407970 • Letter: A
Question
A pendulum, suspended at the origin, consists of two non-
conducting massless rods rigidly connected to each other at
the right angle at the center of the lower rod. The lower rod
has two small metal spheres rigidly attached to it at the ends.
The distance between the centers of those spheres is d . The
length of the vertical rod isL and it is much larger than d .
The total mass of both spheres is m . Gravity acts vertically
against y-axis. External uniform electric field is applied
parallel to the x-axis. Spheres have no excess charges
(initially).
(a) if external uniform electric field, of magnitude E0, is
applied against x-axis, and the spheres are briefly connected
by a short small metal wire (along the rod), what will the
resulting distribution of charges be (qualitatively)? How does
it change when the wire connector is being removed? How
does it change if electric field is turned off after the wire was
removed? [2 pts.]
Now, assume that the procedure of (a) is performed. After
that an external uniform electric field is applied along the
x-axis.
(b) Find the period T of small osculations about the
equilibrium position as a function of all relevant parameters.
Can the frequency omega of small oscillations vanish? If so what
does this mean? [5 pts.]
(c) What happens when electric field E becomes very strong.
Find the equilibrium position and the period of small
oscillations in this case [3 pts.]
(d) How to measure/calculate the values of all charges and
the magnitude of , by measuring period of small
oscillations for known . Provide the relation between E0
and charges as the part of your answer. [5 pts.]
Explanation / Answer
a)when connected two spheres with a connector charge will distributed equally.when connector removed charge will be same. If E0 is zero,charges are moving in random motion net charge will be zero.In above case charges are moving with drift velocity in right direction.
if E0 is along x- axis charges are drifted in left direction
b)T=2*pi*sqrt(L/g).if w vanish T=0
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