1. When is a p-n junction diode reverse biased? The p-n junction diode reverse biased when the source is connected with the positive to the n-side of the diode and the negative to p-side. 2. What is breakdown voltage? Breakdown voltage is the minimum voltage necessary to force an insulator to conduct some amount of electricity. 3. What is zener effect? Zener effect is a type of electrical breakdown in reverse biased of diode in which there is sudden increase of current 4. Give some examples of impurities which are used to make a p-type semiconductor? Aluminum or boron 5. Give some example of impurities which are used to make the n-type semiconductor?  Phosphorus or arsenic 6. What is majority charge carrier in N-type semiconducting material? Electrons are majority charge carrier in N-type semiconducting material. 7. How do sky wave travel?  sky waves are transmitted skyward at some angle from transmitting antenna when they reach ionosphere they reflected back to ground to the receiving antenna. 8. What is majority charge carrier in P-type semiconducting material?  Holes are majority charge in p-tpr semiconducting material 9. What is minority charge carrier in N-type semiconducting material?  Holes 10. What is minority charge carrier in P-type semiconducting material?  Electrons 11. When is a junction diode forward biased? when the source is connected with the positive to p-side of the diode and the negative to N-side of the diode. 12. What happen when forward voltage is applied across the diode? when forward biased is applied across the diode the current at fist increase slowly. 13. What happen when the reverse voltage is applied across the diode? when the reverse voltage is applied across the diode there is almost no current flow, diode conducts badly. 14. Nếu 2 tinh thể bán dẫn một loại P và một loại N được ghép với nhau lớp tiếp giáp PN được hình thành. if two crystal semiconductors one of N-type and one of P-type are joined together the PN junction is formed. 15. Khi diode phân cực thuận lúc đầu dòng tăng chậm  when the diode forward biased the current at fist increase slowly. 16. Khi diode phân cực ngược hầu như không có dòng chảy qua, diode dẫn điện kém. when diode reverse biased there is almost no current flow, the diode conducts badly. 17. Tuy nhiên có một dòng dò ngược nhỏ, dòng dò này vẫn còn tăng mạnh tới hằng số trừ khi có một điện áp đánh thủng đạt được.  however there is small reverse leakage current this leakage current remains substantially constant until what is know as breakdown voltage is reached. 18. Điot thường không bao giờ hoạt động ở vùng đánh thủng nhưng diot zener được thiết kế để tận dụng hiện tượng đánh thủng.  Normal diode is never operated in breakdown region but zener diode is designed to make use of breakdown phenomenon. 19. What is leakage current?  Leakage current is a current flowing thought pn junction when the diode is reverse biased. 20. Asen là một trong những tạp chất có thể được dùng để tạo bán dẫn loại N  Asenic is one of impurities that can create N-type semiconductor. 21. Bo là một trong những tạp chất có thể được dùng để tạo vật liệu bán dẫn loại p Boron is one of impurities that can creat p type semiconducting material. 22. Silic và Ge là 2 nguyên tố được dùng để tạo transistor.  silicon and germanium is two elements used make to transistor. 23. What is rectification?  Rectification is process which charges alternating current into directing current. 24. Để tạo ra bán dẫn loại N người pha tạp silic với nguyên tố nhóm 5 trong bảng hệ thống tuần hoàn.  To make N type semiconductor people doping silicon with 25. How do sky wave travel?  sky waves are transmitted skyward from transmitting antenna when they reach ionosphere they are reflected back to ground to receiving antenna. 26. How do ground wave travel?  ground waves travel around surface of earth for short distances 27. How do space wave?  space waves travel in a direct line from transmitting antenna to receiving antenna 28. What is maximum usable frequency?  high frequency 29. What influences the bending effect in the ionosphere?  the frequency of signal and the angle of radiation 30. What is attenuation?  in process propagation of waves energy of them are lost, it is called attenuation 31. What frequencies are propagated by space wave?  VHF,UHF and microwave are propagated by space wave 32. Name two ways in which space wave travel?  space waves can travel in a direct line from transmitting antenna to receiving antenna or can travel after reflect from the earth’s surface to the troposphere of earth 33. What range have space wave? space waves are 34. What controls sky wave propagation?  ionosphere controls sky wave propagation 35. What is ionosphere?  ionosphere is a part of upper atmosphere which consist of layer of air molecules stretching about 80km above the earth to 500km 36. How do sky waves cover great distances?  Sky waves cover great distances by successive reflect. 37. Name two factors which determine the bending effect of the ionosphere?  the frequency of signal and the angle of radiation. 38. Khúc xạ là hiện tượng đổi hướng đường đi của song điện từ khi lan truyền trong môi trường không đồng nhất  refraction is a phenomenon redirect path of electromagnetic when it propagates in heterogeneous environment. 39. Pha một lượng nhỏ phốt pho và silic thì có thể tạo ra bán dẫn loai N  Doping a litter phosphorus and silicon can be create N-type semiconductor. 40. What is modulation?  Modulation is a technique which charges one or more parameter of carrier wave. 41. Which three quantities of a wave can be modulated?  Frequency, amplitude and phase. 42. Why is frequency modulation better than amplitude modulation?  Because with frequency modulation signal will be not noise and distort. 43. What is modulating signal?  Modulating signal is a signal which carries information. 44. What is frequency modulation?  Frequency modulation is a technique modulation where frequency of carrier wave is charged according amplitude of modulating signal while amplitude and phase are kept const. 45. What is amplitude modulation?  Amplitude modulation is a technique modulation where amplitude of carrier wave is charged according amplitude of modulating wave while frequency and phase are kept const. 46. The two factors which affect the attenuation of ground wave?  the frequency of signal and the nature of surface of earth 47. Phản xạ là hiện tượng khi sóng lan truyền tới bề mặt tiếp xúc của 2 môi trường khác nhau bị đổi hướng và quay trở lại môi trường mà nó đã truyền tới.  reflect is phenomenon when waves propagate to junction of two other environments they are redirected back to environment which they are propagated.