A string with fixed ends is made to go into standing wave patterns. At a given tension, the lowest frequency for which such a pattern exists is 150 Hz. Which of the following frequencies would also cause a standing wave pattern in this case?
a. 250 Hz
b. 500 Hz
c. 750 Hz
d. All of the above frequencies will cause a standing wave pattern in this case.
[Ques. 2] A rectangular loop (area = 0.250 m2) turns in a uniform magnetic field with B = 0.210 T. At an instant when the angle between the magnetic field and the normal to the plane of the loop is /2 rads and increasing at the rate of 0.530 rad/s, what is the magnitude of the emf induced in the loop?
a. 5.25E2 V
b. zero
c. 2.78E2 V
d. 9.91E2 V
e. 1.47E2 V
[Ques. 3] A C note (f = 256 Hz) is sounded on a piano. If the length of the piano wire is 1.8 m and its mass density is 2.2 g/m, what is the tension in the wire?
a. 6.4E+1 N
b. 1.4E+2 N
c. 1.9E+3 N
d. 1.1E+3 N
e. 5.6E+2 N
[Ques. 4] An electric motor draws a current of 2.60 A from a 18.0-V battery when it runs at normal speed. If the motor's armature is jammed so that it cannot rotate, the current suddenly rises to 10.0 A. What is the back emf of the motor when running at normal speed?
a. 4.68 V
b. 10.0 V
c. 22.7 V
d. 13.3 V
e. 133 V
[Ques. 5] For a standing wave on a string the wavelength must equal
a. the distance between adjacent nodes.
b. the distance between adjacent antinodes.
c. twice the distance between adjacent nodes.
d. the distance between supports.
[Ques. 6] A 580-turn circular coil with an area of 0.0550 m2 is mounted on a rotating frame, which turns at a rate of 17.0 rad/s in the presence of a 0.0400-T uniform magnetic field that is perpendicular to the axis of rotation. What is the instantaneous emf in the coil at the moment that the normal to its plane is at a 50.0 angle to the field?
a. zero
b. 21.7 V
c. 18.9 V
d. 16.6 V
e. 0.0751 V
[Ques. 7] A 1.30-m string is held fixed at both ends. When driven by a 140-Hz source, the string vibrates in 4 distinct segments. What is the natural fundamental frequency of the string?
a. 35.0 Hz
b. 70.0 Hz
c. 215 Hz
d. 431 Hz
e. 45.5 Hz
[Ques. 8] A 420-turn circular coil with an area of 0.0650 m2 is mounted on a rotating frame, which turns at a rate of 22.3 rad/s in the presence of a 0.0550-T uniform magnetic field that is perpendicular to the axis of rotation. What is the instantaneous emf in the coil at the moment that the normal to its plane is perpendicular to the field?
a. 33.5 V
b. zero
c. 0.0673 V
d. 747 V
e. 1.50 V
[Ques. 9] A standing wave is set up in a 200-cm string fixed at both ends. The string vibrates in 8 distinct segments when driven by a 120-Hz source. What is the wavelength?
a. 6 cm
b. 13 cm
c. 25 cm
d. 50 cm
e. 100 cm
[Ques. 10] A motor has an internal resistance of 12.0 . When running, the motor has a back emf of 29 V and draws a current of 3.7 A. What is the supply voltage in this case?
a. 29 V
b. 44 V
c. 73 V
d. 15 V
e. 32 V
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