推 ajujgrua:被搶了T_T 01/30 19:08
課程名稱︰普通物理甲
課程性質︰必修
課程教師︰陳政維
開課學院：工學院
開課系所︰工程科學與海洋工程學系
考試日期（年月日）︰2007/1/16
考試時限（分鐘）：120
是否需發放獎勵金：是
（如未明確表示，則不予發放）
試題 :
1. Two identical conducting spheres, fixed in place, attract each other
with an electrostatic force of 0.108 N when their center-to-center
separation id 50.0cm. The spheres are then connected by a thin conducting
wire. When the wire is removed, the spheres repel each other with an
electrostatic force of 0.0360N. Of the initial charge on the spheres,
with a positive net charge, what was (a) the negative charge on one of
them and (b) the positive charge on the other?
2. Figure 2 shows the deflecting plates of an ink-jet printer, with
superimposed coordinate axes. An ink drop with a mass m of 1.3*10^(-10)
kg and a negative charge of magnitude Q= 1.5*10^(-13) C enters the region
between the plates, initially moving along the x axis with speed v =20m/s.
x
The length L of each plate is 1.6cm. The plates are charged and thus
produce an electric field at all points between them. Assume that field E
is downward directed, is uniform, and has a magnitude of 1.4*10^6 N/C.
What is the vertical deflection of the drop at the far edge of the plates?
(The gravitational force on the drop is small relative to the electrostatic
force acting on the drop and can be neglected)
y plate
↑========================================
∣
∣
∣
∣ 20m/s
——●——→————————————————————→ x
∣
∣========================================
L
3. A solid nonconducting sphere of redius R=5.60cm has a nonuniform charge
distribution of volume charge density ρα r^(2)/R, where r is radial
distance from the sphere's center. What is the magnitude E of the electric
field at (a) r=0, (b) r=R/2.00, and (c)r=R?
4. What is the electric field E at a point P(r,θ,ψ) due to an electric
dipole? (r>>d, d is the distance of the diploe)
↑
∣ ● P (r,θ,ψ)
∣ ／
∣ ／
∣ ∫∫
∣ ／
Q － ／
∣／
∣
-Q －
∣
∣
5. A parallel-plate capacitor whose capacitance is 15.0 pF is charged by
a battery to a potential difference V= 12.0 V between its plates. The
charging battery is now disconnected, and a porcelain slab(κ=6.0)
is slipped between the plates. What is the potential energy (a) of
the capacitor before the slab is inserted and (b) of the capacitor-slab
device after the slab is inserted?
6. Current is set up through a truncated right circular cone of resistivity
731 Ω-m, left radius a=2.00mm right radius b=2.30mm, and length L=1.94cm.
Assume that the current density is uniform across any cross section taken
perpendicular to the length. What is the resistance of the cone?
7. A 3.00MΩ resistor and a 1.00mF capacitor are connected in series with
an ideal battery of emfξ=4.00V. At 1.00s after the connection is made,
what is the rate at which (a) energy is being stored in the capacitor and
(b) energy is being delivered by the battery?
8. A straight, horizontal length of copper wire has a current i=28A through
it. What are the magnitude and direction of the minimum magnetic field B
needed to suspend the wire that is, to balance the gravitational force
on it? The liner density (mass per unit length) of the wire is 46.6g/m.
9. A positron with kinetic energy 2.00keV is projected into a uniform
magnetic field B of magnitude 0.100T, with its velocity vector making
an angle of 60.0 度 with B. Find (a) the period and (b) the pitch p of
its helical path.
10. A long conducting cylinder with inner radius a=1.0cm and outer radius
b=4.0cm. The cylinder carries a current out of the page, and the
magnitude of the current density in the cross section is given by
J=cr^2, with c=3.0*10^6 A/m^4 and r in meters. What is the magnetic field
B at a point that is 3.0cm form the central axis of the cylinder?
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