In automobiles, brass radiators have been replaced with aluminum ones to reduce weight. Assume that the wall thickness in each radiator is 0.5 mm, the engine fluid is at a temperature of 400 K, and the ambient air temperature is 300 K.
(a) Calculate the heat flux for each radiator material.
(b) Estimate the relative area in % and the relative weight of changing from a brass radiator to an aluminum radiator, assuming the same heat transfer rate (dQ/dt) for both designs and that the brass is 30 weight %zinc and 70 weight %copper with a density of 8.4 g/cm3.
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Camera Exposure: If a camera lens aperture is set to f/4, then
A. the radius of the lens aperture is ¼ the focal length. B. the focal length of the lens is 4 mm. C. the diameter of the lens aperture is ¼ the focal length. D. the radius of the lens aperture is 4 times its focal length. E. the diameter of the lens aperture is 4 times its focal length.
The Richter magnitude scale is logarithmic, each 1-point increase on the scale corresponds to a
A) 100-fold increase in the amplitude of ground shaking. B) 30-fold increase in the amplitude of ground shaking. C) 10-fold increase in the amplitude of ground shaking. D) an increase of 30 times the energy for each magnitude.
A parallel plate capacitor of capacitance C0 has plates of area A with separation d between them. When it is connected to a battery of voltage V0, it has charge of magnitude Q0 on its plates. It is then disconnected from the battery and the plates are pulled apart to a separation 2d without discharging them. After the plates are 2d apart, the new capacitance and the potential difference between the plates are what?
A.
C0, 
V0B.
C0, V0C.
C0, 2V0D.
E.
If an AC circuit consists of a 220 mH inductor in series with a 75 k
resistor and an AC generator with rms voltage of 12 V. If the frequency of the generator is 25 kHz, what is the rms voltage drop across the inductor?
A. 7.0 V B. 2.6 V C. 9.4 V D. 5.0 V