Final_Exam_12_11_07_Solns

Final_Exam_12_11_07_Solns - PHYSICS 222 FALL 2007 FINAL...

Info iconThis preview shows pages 1–4. Sign up to view the full content.

View Full Document Right Arrow Icon
PHYSICS 222 FALL 2007 FINAL EXAM SOLUTIONS TUESDAY, DECEMBER 11, 2007 Problems 61-80 are worth 4 points each 61. An 80-turn circular coil of radius 5.00 cm carries a current of 5.00 Amperes and lies in the x-y plane as shown in the figure. As viewed from the top (i.e., from the positive z-axis), the current is circulating in the coil in the clockwise direction. The magnetic field at the center of the coil is ____ . x y z coil A. (100 mT) k ˆ B. (100 mT) k ˆ C. (5 mT) k ˆ D. (5 mT) k ˆ E. (50 mT) k ˆ From the circular right-hand rule, the direction of the magnetic field at the center of the coil is in the k ˆ direction. The magnitude of the field is B = µ o NI 2R = (4 π × 10 7 T·m/A)(80)(5.00 A) 2(0.0500 m) = 5.03 × 10 3 T = 5.03 mT . 62. An ac current flows through an ideal inductor with an inductance of 2.11 mH. The current through the inductor is given by i(t) = (2.50 A) cos[(380 rad/s)t], where t is the time in seconds. The amplitude of the ac voltage across the inductor is ____ Volts. A. 1 B. 2 C. 3 D. 4 E. 5 V L = IX L = I ω L = (2.50 A)(380 rad/s)(2.11 × 10 3 H) = 2.00 Volts
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
63. The wave function of a transverse wave on a stretched string is given by y(x,t) = (1.00 mm) cos[(126 rad/m)x] cos[(500 rad/s)t] . The wave is a ____ wave with a wavelength of ____ . A. standing, 0.050 m B. traveling, 0.010 m C. standing, 0.10 m D. traveling, 0.20 m E. standing, 0.15 m From the form of the wave function where the x and t dependences are separated into two sinusoidal functions, the wave is a standing wave. The wavelength is λ = 2 π k = 2 π 126 rad/m = 0.050 m . 64. A plane electromagnetic traveling wave in vacuum is polarized along the x-axis, has a wavenumber k, and moves in the positive y direction. If the amplitude of the electric field wave is designated as E 0 , a possible wave function of the electric field wave in the electromagnetic wave is ____ . (x, y, and z are Cartesian coordinates, c is the speed of light in vacuum, and t is the time) A. E 0 cos(kx ct) i ˆ B. E 0 sin(kx + ct) j ˆ C. E 0 sin[k(y ct)] i ˆ D. E 0 cos[k(y + ct)] k ˆ E. E 0 cos(kz ct) k ˆ For a traveling plane wave moving in the +y direction, the argument of the sinusoidal function has to be (ky ω t), where here ω = ck. Thus the argument becomes [k(y ct)]. The electric field axis is the axis of polarization of the wave, which here is the x-axis. Therefore the answer is C. 65. A microscope has an objective lens with a focal length of 1.00 cm and an eyepiece with a focal length of 2.50 cm. A small object to be viewed is 1.20 cm in front of the objective lens. The angular magnification of the microscope is ____ . A. 20 B. 30 C. 40 D. 50 E. 60 1 s 1 ' = 1 f 1 s 1 = 1 1.00 cm 1 1.20 cm = 1 6.00 cm , so s 1 ' = 6.00 cm . M = (25 cm)s 1 ' f 1 f 2 = (25 cm)(6.0 cm) (1.00 cm)(2.50 cm) = 60 .
Background image of page 2
66. Monochromatic light of wavelength 500 nm is normally incident on a diffraction grating with 5000 lines per cm. The second-order diffraction peak occurs at a diffraction angle of ____ degrees. A. 30 B. 40 C. 50 D. 60 E. 70 d = 0.01 m 5000 = 2.00 × 10 6 m . sin θ = m λ d = 2(5.00 × 10 7 m) 2.00 × 10 6 m = 1 2 , so θ = 30˚ .
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 4
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 02/11/2012 for the course PHYSICS 222 taught by Professor Ogilvie during the Fall '05 term at Iowa State.

Page1 / 11

Final_Exam_12_11_07_Solns - PHYSICS 222 FALL 2007 FINAL...

This preview shows document pages 1 - 4. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online