A Nichrome wire has a radius of 0.50 mm and a resistivity of 1.5 10-6 Wm. If the wire carries a current of 1.0 A, what is the potential difference per unit length along this wire?
a. 1.9 V/m
c. 1.6 V/m
b. 0.95 V/m
d. 0.003 V/m
[Ques. 2] A solid sphere, a solid cylinder, and a hoop each have the same mass and radius. If they are spinning at the same angular velocity, which one has the greatest rotational kinetic energy?
a. the sphere
b. the cylinder
c. the hoop
d. They all have the same rotational kinetic energy.
[Ques. 3] A 0.10-m long metal rod has a radius of 1.0 cm and a resistance of 3.2 10-5 W. What is the resistivity of the metal?
a. 5.0 10-8 Wm
c. 10 10-8 Wm
b. 160 10-8 Wm
d. 1.6 10-8 Wm
[Ques. 4] A bus is designed to draw its power from a rotating flywheel that is brought up to its maximum speed (3000 rpm) by an electric motor. The flywheel is a solid cylinder of mass 250 kg and radius 0.500 m (Icylinder = MR2/2). If the bus requires an average power of 10.0 kW, how long will the flywheel rotate?
a. 154 s
c. 463 s
b. 308 s
d. 617 s
[Ques. 5] Two wires with the same resistance have the same diameter but different lengths. If wire 1 has length L1 and wire 2 has length L2, how do L1 and L2 compare if wire 1 is made from copper and wire 2 is made from aluminum? The resistivity of copper is 1.7 105 Wm and the resistivity of aluminum is 2.82 105 Wm.
a. L1 = 0.36 L2
c. L1 = 0.60 L2
b. L1 = 2.8 L2
d. L1 = 1.7 L2
[Ques. 6] An initially installed flywheel can store 106 J of kinetic energy when rotating at 300 rad/s. It is replaced by another flywheel of the same size but made of a stronger material. If its mass is the same as that of the original, and it is now capable of achieving a rotational speed of 600 rad/s, what maximum energy can be stored?
a. 40 105 J
c. 10 105 J
b. 20 105 J
d. 5.0 105 J
[Ques. 7] How long is a wire made from 200 cm3 of copper if its resistance is 8.5 ohms? The resistivity of copper is 1.7 105 Wm.
a. 10 m
c. 7.1 m
b. 2.2 102 m
d. 3.0 103 m
[Ques. 8] A rotating flywheel can be used as a method to store energy. If it has 2.0 106 J of kinetic energy when rotating at 400 rad/s, and if a frictional torque of 4.0 Nm acts on the system, in what interval of time would the flywheel come to rest?
a. 3.5 min
c. 14 min
b. 42 min
d. 21 min
[Ques. 9] Two cylindrical resistors are made of the same material and have the same resistance. The resistors, R1 and R2, have different radii, r1 and r2, and different lengths, L1 and L2 . Which of the following relative values for radii and lengths would result in equal resistances?
a. r1 = r2 and 4L1 = L2
c. 2r1 = r2 and 4L1 = L2
b. r1 = r2 and L1 = 2L2
d. 2r1 = r2 and L1 = 2L2
[Ques. 10] A rotating flywheel can be used as a method to store energy. If it is required that such a device be able to store up to a maximum of 2.00 106 J when rotating at 400 rad/s, what moment of inertia is required?
a. 50 kgm2
c. 12.5 kgm2
b. 25 kgm2
d. 6.3 kgm2
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