A system is acted on by its surroundings in such a way that it receives 80 J of heat while simultaneously doing 20 J of work. What is its net change in internal energy?
a. 100 J
b. 60 J
c. zero
d. 60 J
e. 100 J
[Ques. 2] Superconductors can carry very large currents with no resistance. If a superconducting wire is formed into a solenoid of length 20.0 cm with 691 turns, what is the magnetic field inside the solenoid when the current is 5.38 kA? (0 = 4 107 Tm/A)
a. 1.86 T
b. 0.934 T
c. 46.7 T
d. 23.4 T
e. 73.4 T
[Ques. 3] In the first law of thermodynamics, U = Q + W, W is positive when
a. the work is being done on the environment by the system.
b. the work is being done on the system by the environment.
c. the work is being done on the environment by the system, and the temperature of the system goes up.
d. the work is being done on the system by the environment, and the temperature of the system goes up.
[Ques. 4] A current in a solenoid with N turns creates a magnetic field at the center of that loop. The field strength is directly proportional to:
a. number of turns in the loop.
b. current strength.
c. Both choices A and B are valid.
d. None of the above are valid.
[Ques. 5] What is the work done on the gas during the compression?
a. 5.9E+3 J
b. 7.5E+3 J
c. 1.5E+4 J
d. 1.8E+4 J
[Ques. 6] A current in a solenoid coil creates a magnetic field inside that coil. The field strength is directly proportional to:
a. the coil area.
b. the current.
c. Both A and B are valid choices.
d. None of the above choices are valid.
[Ques. 7] What is the final temperature of the gas?
a. 123 C
b. 150 C
c. 27.6 C
d. 59.3 C
[Ques. 8] A solenoid with 568 turns, 0.19 m long, carrying a current of 3.5 A and with a radius of 102 m will have what strength magnetic field at its center? (magnetic permeability in empty space 0 = 4 107 Tm/A)
a. 1.2E1 T
b. 3.3E3 T
c. 2.5E3 T
d. 1.3E2 T
e. 4.1E2 T
[Ques. 9] The volume of a gas changes from 0.750 m3 to 0.320 m3 at a constant pressure of 1.5 105 Pa. How much work is done by the gas on its environment?
a. 4.8E+4 J
b. 6.5E+4 J
c. 4.8E+4 J
d. 6.5E+4 J
[Ques. 10] Two parallel wires carry a current I in the same direction. Midway between these wires is a third wire, also parallel to the other two, which carries a current 0.5 I, but in the direction opposite from the first two wires. In which direction are the net forces on the outer wires?
a. Since the net forces are zero, there is no direction.
b. Both forces are toward the center wire.
c. Both forces are away from the center wire.
d. Both forces on the two wires are in the same direction in space.
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