A 45-mH inductor is connected in series with a 60-? resistor through a 15-V dc power supply and a switch. If the switch is closed at t = 0 s, what is the current after 7.0 ms?
A)
250 mA
B)
650 mA
C)
550 mA
D)
280 mA
E)
850 mA
A
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A European sports car dealer claims that his product will accelerate at a constant rate from rest to a speed of 100 km/hr in 9.00 s. What distance will the sports car travel during the 9.00 s acceleration period? (Hint: First convert speed to m/s.)
a. 55.5 m c. 111 m b. 125 m d. 250 m
Assume that all air properties may be evaluated at 27°C and determine the constants in the correlation equation: Nu = C (Gr Pr)m
A laboratory experiment has been performed to determine the natural-convection heat
transfer correlation for a horizontal cylinder of elliptical cross section in air. The
cylinder is 1-m-long, has a hydraulic diameter of 1 cm, a surface area of 0.0314 m2, and
is heated internally by electrical resistance heating. Recorded data include power
dissipation, cylinder surface temperature, and ambient air temperature. The power
dissipation has been corrected for radiation effects:
GIVEN
• A horizontal, elliptical cylinder in air
• Hydraulic diameter (Dh) = 1 cm = 0.01 m
• Length (L) = 1 m
• Cylinder surface area (As) = 0.0314 m2
• Experimental data for (Ts – T?) and q shown above FIND
• The constants in the correlation equation Nu = C(Gr Pr)m
ASSUMPTIONS
• All air properties may be evaluated at 27°C
SKETCH
PROPERTIES AND CONSTANTS
for dry air at 27°C
Thermal expansion coefficient (?) = 0.00333 1/K
Thermal conductivity (k) = 0.0256 W/(m K)
Kinematic viscosity (?) = 16.4 × 10–6 m2/s
Prandtl number (Pr) = 0.71
A potential energy function is given by U(x) = (3.00 N)x + (1.00 N/m2)x3. What is the force that is associated with this potential energy function?
A) 3.00 N + (1.00 N/m2)x2 B) -3.00 N - (3.00 N/m2)x2 C) (-0/500 N/m2)x2 + (-1.00 N/m2)x4 D) (0.500 N/m2)x2 + (1.00 N/m2)x4 E) -3.00 N - (1.00 N/m2)x2
A 500 nm light is reflected constructively from a thin layer of oil of index of refraction 1.25, which rests on the top of water of index of refraction 1.33. What is the minimum thickness of the layer of oil?
A) 100 nm B) 150 nm C) 175 nm D) 200 nm E) 225 nm