Energy in Capacitors: Two parallel plates that are initially uncharged are separated by 1.7 mm, have only air between them, and each have surface areas of 16 cm2. How much charge must be transferred from one plate to the other if 1.9 J of energy are to be stored in the plates? (?0 = 8.85 × 10-12 C2/N ? m2)
A. 5.6 ?C
B. 4.0 ?C
C. 8.0 ?C
D. 0.60 mC
Answer: A
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A long 1-cm-diameter electric copper cable is embedded in the center of a 25 cm square concrete block. If the outside temperature of the concrete is 25°C and the rate of electrical energy dissipation in the cable is 150 W per meter length, determine the temperatures at the outer surface and at the center of the cable.
GIVEN
FIND
The temperatures at the outer surface (Ts) and at the center of the cable (Tc)
ASSUMPTIONS
Two dimensional, steady state heat transfer
Uniform thermal conductivities
SKETCH
Standing Sound Waves: In a resonating pipe that is open at one end and closed at the other end, there
A. are displacement nodes at each end. B. are displacement antinodes at each end. C. is a displacement node at the open end and a displacement antinode at the closed end. D. is a displacement node at the closed end and a displacement antinode at the open end.
If a person's eyeball is too short from front to back, the person is likely to suffer from
A) astigmatism. B) spherical aberration. C) chromatic aberration. D) farsightedness. E) nearsightedness.
A engine goes through a cyclic process. During the cyclic process the engine does 600 J of work and has a heat output of 2400 J. What is the efficiency of the engine?
A. 10% B. 20% C. 35% D. 55% E. 62%