The most widely accepted system of measurement is the metric system
a. True
b. False
Indicate whether the statement is true or false
True
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In the experimental determination of the heat transfer coefficient between a heated steel ball and crushed mineral solids, a series of 1.5% carbon steel balls were heated to a temperature of 700°C and the center temperature-time history of each was measured with a thermocouple as it cooled in a bed of crushed iron ore that was placed in a steel drum rotating horizontally at about 30 rpm. For a 5-cm-diameter ball, the time required for the temperature difference between the ball center and the surrounding ore to decrease from 500°C initially to 250°C was found to be 64, 67, and 72 s, respectively, in three different test runs. Determine the average heat transfer coefficient between the ball and the ore. Compare the results obtained by assuming the thermal conductivity to be infinite
with those obtained by taking the internal thermal resistance of the ball into account.
GIVEN
Heat steel balls are put in crushed iron ore
Balls are 1.5% carbon steel balls
Initial temperature of balls (To) = 700°C
Ball diameter = 5 cm = 0.05 m
Temperature difference between the ball center and the ore
Center temperature of the balls decreases from 500°C to 250°C
Time taken was found to be 64, 67, and 72 s, respectively, in three different test runs
FIND
The average heat transfer coefficient between the ball and the ore.
Compare the results obtained
(a) by assuming the thermal conductivity to be infinite with
(b) those obtained by taking the internal thermal resistance of the ball into account
ASSUMPTIONS
Temperature of the iron ore is uniform and constant
SKETCH
When the accelerating voltage in an X-ray tube is doubled, the minimum wavelength of the X-rays
A) is increased to twice the original value. B) is increased to four times the original value. C) is decreased to one-fourth the original value. D) is decreased to one-half the original value.
In each of the following situations, point charge q moves in a uniform magnetic field B. The strength of the magnetic field is indicated by the density of field lines. In each situation, the initial speed v of the charge is the same. For which situation(s) will the charge q have the largest displacement in a certain time T?
Which variable is increasing the fastest on the graph prepared in Procedure 2?