# application of Ohm’s law

1. What is the wavelength in meters of radio waves produced by a radio station with a frequency of 1400 kHz?

2. A series of ocean waves, each 6.0 m from crest to crest, moving past an observer at a rate of 2.0 waves per second, has what speed?

3. What are the wavelength limits in meters of the audible region of the sound spectrum ( v = 344 m/s)?

4. How many times greater is the speed of red light ( λ = 700 nm) than the speed of violet light ( λ = 400 nm) in a vacuum?

5. The intensity of a 70-dB whistle is doubled. What is the new dB level?

6. A particular sound with large intensity is reduced 1000-fold. What is the dB reduction?

7. The speed of light in diamond is 1.24 × 10 8 m/s. What is the index of refraction of diamond?

8. A particular material has an index of refraction of 1.25. What percent of the speed of light in vacuum is the speed of light in the material?

9. An object is placed 20 cm in front of a concave spherical mirror. Give the general characteristics of the image for a mirror with a radius of curvature of R = 30 cm.

10. A plane mirror stands vertically on a table. A ruler lies on the table in such a position as to make an angle of 30 ° with the mirror. Determine the angle between the ruler and its image.

11. An object is placed 20 cm from a converging spherical lens. Give the general characteristics of the image for a lens with a focal length of f = 25 cm.

12. An insulator has a positive electric charge of 2.4 × 10 <sub>-17</sub> C. How many electrons were added or removed?

13. If two protons are moved 3 times farther apart, the electrical force between them is what factor of the original force?

14. A steady current of 0.15 A exists in a wire for 20 s. How much net charge passes by a point in the wire?

15. How many electrons does the charge from Question 14 represent?

16. A current of 6.0 A flows through a resistance of 50 ohm. How much power is dissipated?

17. A 20 ohm resistor and a 30 ohm resistor are wired in parallel and connected to a 9.0-V battery. How much current is drawn from the battery?

18. Three resistors, 10, 20, and 30 ohms, are wired in series and connected to a 120-V battery. How much current flows in the circuit?

19. A doorbell has an input voltage of 120 V. A transformer that steps the voltage down to 12 V has 500 turns on its primary. What is the number of turns on the secondary?

20. The voltage in a house is measured to be 122.5 V. What is the current drawn by a 75.0-W light bulb?