| 6, 7, MP1, 26,
MP2 = 67 a, b, c, d only, 24, 32, 33, 28, 49, 51, 53 |
6. (a) Number
of atoms =(mass/molar mass)*NA, where NA =
Avogadro's number and mass = density*volume. Density =
8900 kg/m3 and volume = 1.00 m3. Molar
mass = 0.064 kg/mole.
(b) You already know the # atoms/m3
from part (a).
( # free electrons)/atom = (# free electrons/m3)/(#
atoms/m3) |
7. (a)
Integrate the current formula; you will obtain an expression
containing t3. Evaluate at the two limits of time and
subtract to get definite integral.
(b) Q = I*time, where I is the contain current you seek. Set this
value of Q to the part (a) result ~~~ Find I. |
MP1.
The potential difference between two points in a wire 75.0 cm
apart is 0.938 (V) when the current density is 4.40 x10 7
A/m2. What are (a) the magnitude of the electric field in the wire
(b) the resistivity of the material of which the wire is made?
I/A = J = 4.40x10 7 A/m2 = E/resistivity
= V/(L*resistivity) using E = V/L, where V is the magnitude of the
voltage difference between the two points in space.
Find resistivity and E. |
| 26. See
SEC. 25.2 on temperature dependences; we assume area A and
length L do not change appreciably during the heating process .
See problem 67 (MP2) discussed next, for a counter example. |
|
MP2: 67 = a, b, c, d only.
(a) Use equation 25. 10; get area A from the formula for a circle
with given diameter.
(b) See equation 25.6.
(c) This question is "off topic" and will be discussed
in detail and /or Physics 4C when you get there.
(d) change in R =
(dR/dL)*(change in L)+
(dR/dA)*(change in A)+
(dR/d rho)*(change in rho ),
where rho = resistivity,
We are given that the change in A = 0 so the
second term in the above sum is ZERO.
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