The resistance of a platinum wire is to be calibrated for low-temperature work. A platinum wire with resistance 1.5 ? at 30°C is immersed in liquid nitrogen at 93 K (?180°C). If the temperature response of the platinum wire is linear, what is the expected resistance of the platinum wire at ?180°C? [?platinum = 3.92 × 10^?3 (°C)?1]
a. 0.265 ?
b. 2.38 ?
c. 2.73 ?
d. 8.48 ?
e. 0.618 ?
a
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An electron moving in the direction of the +x-axis enters a magnetic field. If the electron experiences a magnetic deflection in the -y direction, the direction of the magnetic field in this region points in the direction of the
A) +z-axis. B) -z-axis. C) -x-axis. D) +y-axis. E) -y-axis.
Consider an atom of gold in which the nucleus contains 79 protons and 118 neutrons. What is its atomic number and atomic mass number?
A) The atomic number is 118, and the atomic mass number is 79. B) The atomic number is 118, and the atomic mass number is 197. C) The atomic number is 79, and the atomic mass number is 197. D) The atomic number is 79, and the atomic mass number is 118.
In the relativistic case, doubling the speed of an electron causes its wavelength to
A) double. B) more than double. C) halve. D) decrease to less than one-half. E) quadruple.
The objective lens of a refracting telescope has a focal length of 60 cm and the eyepiece a focal length of 8.0 cm. What is the angular magnification of the telescope?
A) 34 B) 480 C) 68 D) 0 E) 7.5