A refrigerator has a performance coefficient (COP) of 1.15, and it extracts 7.95 J of heat from the cold reservoir during each cycle
(a) How much work is done on the gas in each cycle?
(b) How much heat is exhausted into the hot reservoir in each cycle?
(a) 6.91 J (b) 14.9 J
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In an AC series circuit the inductive reactance is 41.0 ? and the frequency is 137 Hz. What is the inductance in the circuit?
a. 4.8E–2 H b. 1.5E–1 H c. 3.0E–1 H d. 4.7E–1 H e. 2.2E–1 H
Two flanged shafts are connected by eight 18-mm bolts. The diam-eter of the bolt circle is 240 mm. The allowable shear stress in the bolts is 90 MPa. Ignore friction between the flange plates. The maximum value of torque T0 is approximately:
(A) 19 kN?m
(B) 22 kN?m
(C) 29 kN?m
(D) 37 kN?m
Boron has primarily two isotopes, one with an atomic mass of 11 amu and another with an atomic mass of 10 amu. If the abundance of the boron atom with a mass
of 11 amu is 18.9 percent and the abundance of the other isotope is 81.1 percent, what would be the average mass of the boron atom? A) 10.19 amu B) 11 amu C) 10 amu D) 10.81 amu E) not enough information given
Two long parallel wires are separated by 6.0 mm. The current in one of the wires is twice the other current. If the magnitude of the force on a 3.0-m length of one of the wires is equal to 8.0 ?N, what is the greater of the two currents?
a. 0.20 A b. 0.40 A c. 40 mA d. 20 mA e. 0.63 A