Chapter 31

1. Chapter 31 Alternating Current Circuits (cont.)

2. Power is supplied to the primary and delivered from the secondary. See Figure 31.21 at the right. • Magnetic flux is confined to the iron core. • Terminal voltages: V2/V1 = N2/N1. • Currents in primary and secondary: V1I1 = V2I2. Transformers

3. Q31.8 In the transformer shown in the drawing, there are more turns in the secondary than in the primary. In this situation, the voltage amplitude is A. greater in the primary than in the secondary. B. smaller in the primary than in the secondary. C. the same in the primary and in the secondary. D. not enough information given to decide

4. A31.8 In the transformer shown in the drawing, there are more turns in the secondary than in the primary. In this situation, the voltage amplitude is A. greater in the primary than in the secondary. B. smaller in the primary than in the secondary. C. the same in the primary and in the secondary. D. not enough information given to decide

5. Q31.9 In the transformer shown in the drawing, there are more turns in the secondary than in the primary. In this situation, the current amplitude is A. greater in the primary than in the secondary. B. smaller in the primary than in the secondary. C. the same in the primary and in the secondary. D. not enough information given to decide

6. A31.9 In the transformer shown in the drawing, there are more turns in the secondary than in the primary. In this situation, the current amplitude is A. greater in the primary than in the secondary. B. smaller in the primary than in the secondary. C. the same in the primary and in the secondary. D. not enough information given to decide

7. Chapter 32 Electromagnetic Waves

8. Maxwell’s equations predict that an oscillating charge emits electromagnetic radiation in the form of electromagnetic waves. • Figure 32.3 below shows the electric field lines of a point charge undergoing simple harmonic motion. Maxwell’s equations and electromagnetic waves

9. The electromagnetic spectrum includes electromagnetic waves of all frequencies and wavelengths. (See Figure 32.4 below.) The electromagnetic spectrum

10. Visible light is the segment of the electromagnetic spectrum that we can see. • Visible light extends from the violet end (400 nm) to the red end (700 nm), as shown in Table 32.1. • Eyes have three kinds of “cones” (cells sensitive to light) • S : ~ 400 – 500 nm • M : ~ 450 – 600 nm • L : ~ 500 – 650 nm Visible light

11. A plane wave has a planar wave front. See Figure 32.5 below. Plane electromagnetic waves

12. The Plane wave satisfies Maxwell’s equations. • Gauss’s Law is illustrated below • Faraday/Ampere’s Laws to the right. A simple plane electromagnetic wave

13. The magnitudes of the fields in vacuum are related by E = cB. • The speed of the waves is c = 3.00 × 108 m/s in vacuum. • The waves are transverse. Both fields are perpendicular to the direction of propagation and to each other. (See Figure 32.9 at the right.) Key properties of electromagnetic waves

14. Figure 32.13 (right) shows the electric and magnetic fields for a sinusoidal wavealong the x-axis. Fields of a sinusoidal wave

15. Q32.1 In a vacuum, red light has a wavelength of 700 nm and violet light has a wavelength of 400 nm. This means that in a vacuum, red light A. has higher frequency and moves faster than violet light. B. has higher frequency and moves slower than violet light. C. has lower frequency and moves faster than violet light. D. has lower frequency and moves slower than violet light. E. none of the above

16. A32.1 In a vacuum, red light has a wavelength of 700 nm and violet light has a wavelength of 400 nm. This means that in a vacuum, red light A. has higher frequency and moves faster than violet light. B. has higher frequency and moves slower than violet light. C. has lower frequency and moves faster than violet light. D. has lower frequency and moves slower than violet light. E. none of the above

17. Waves passing through a small area far from a source can be treated as plane waves. (See Figure 32.12 at the right.) Sinusoidal electromagnetic waves

18. Q32.2 At a certain point in space, the electric and magnetic fields of an electromagnetic wave at a certain instant are given by This wave is propagating in the positive x-direction. negative x-direction. C. positive y-direction. D. negative y-direction. E. none of the above

19. A32.2 At a certain point in space, the electric and magnetic fields of an electromagnetic wave at a certain instant are given by This wave is propagating in the positive x-direction. negative x-direction. C. positive y-direction. D. negative y-direction. E. none of the above

20. Q32.3 A sinusoidal electromagnetic wave in a vacuum is propagating in the positive z-direction. At a certain point in the wave at a certain instant in time, the electric field points in the negative x-direction. At the same point and at the same instant, the magnetic field points in the positive y-direction. negative y-direction. C. positive z-direction. D. negative z-direction. E. none of the above

21. A32.3 A sinusoidal electromagnetic wave in a vacuum is propagating in the positive z-direction. At a certain point in the wave at a certain instant in time, the electric field points in the negative x-direction. At the same point and at the same instant, the magnetic field points in the positive y-direction. negative y-direction. C. positive z-direction. D. negative z-direction. E. none of the above

22. Q32.4 In a sinusoidal electromagnetic wave in a vacuum, the electric field has only an x-component. This component is given by Ex = Emax cos (ky + wt) This wave propagates in the A. positive z-direction. B. negative z-direction. C. positive y-direction. D. negative y-direction. E. none of the above

23. A32.4 In a sinusoidal electromagnetic wave in a vacuum, the electric field has only an x-component. This component is given by Ex = Emax cos (ky + wt) This wave propagates in the A. positive z-direction. B. negative z-direction. C. positive y-direction. D. negative y-direction. E. none of the above