ELECTRICITY and MAGNETISM

1. ELECTRICITY and MAGNETISM

2. NỘI DUNG MÔN HỌC Chương 1. Trường tĩnh điện Chương 2. Vật dẫn trong điện trường Chương 3. Dòng điện không đổi Chương 4. Từ trường tĩnh Chương 5. Cảm ứng điện từ

3. TÍNH ĐIỂM MÔN HỌC Điểm thường kỳ: là tổ hợp của: Bài kiểm tra trên lớp. Chuyên cần. Thái độ học tập. Điểm chấp nhận phải từ 3 trở lên. Lưu ý: không nghỉ học buổi nào, thái độ học tập tốt, không vi phạm qui chế sẽ được cộng thêm từ 1 đến 1,5 điểm TK và nếu điểm giữa kỳ nhỏ hơn 4, lớn hơn hoặc bằng 3 vẫn được dự thi cuối kỳ.

4. Thi giữa kỳ: Nội dung thi: Chương1,2. Hình thức thi: Trắc nghiệm và tự luận, thời gian 45’. Thời gian thi: Dự kiến vào tuần thứ 7 (thực học). Điểm đạt 4 trở lên (thi một lần duy nhất) Thi cuối kỳ: Nội dung thi: Chương 3,4 Hình thức thi: Trắc nghiệm và tự luận, thời gian 60’ Điểm đạt 4 trở lên (thi một lần duy nhất)

5. Điều kiện để được thi cuối kỳ: Mắc phải một trong những điều sau đây sẽ không được dự thi cuối kỳ: Nghỉ quá 20% tổng số tiết học ( quá 6 tiết). Điểm thi giữa kỳ nhỏ hơn 3. Điểm thường kỳ dưới 3.

6. Chapter 1ELECTRIC FIELDS

8. 1 – Properties of electric charges 2 – Coulomb’s Law 3 – The electric field 4 – Electric field lines

9. 1 – Properties of electric charges -There are two kinds of charges in nature : charge positive and charge negative.

11. - Charges of the same sign repel one another and charges with opposite signs attract one another.

12. - Total charge in an isolated sytems is conserved - Electric charge has the smallest value is call element charge. q = Ne where N is some interger e = -1,6.10-19C me = 9,1.10-31kg

13. 2 – Coulomb’s Law

14. Electric force between two stationary charged particles:

15. Electric force between two stationary charged particles: k = 9.109 (Nm2/C2) Coulomb constant r : space between two point charges (m) is known as the permitivity of free space

16. Exercise There are two point electric charges: q1 = -3.10-8C at A, q2 = 5.10-8C at B, for from AB = 10cm. Find the electric force exerted by q1 on q2? The electric force exerted by q1 on q2 is:

17. To calculate the electric force due to a group of point charges, the vector sum of the electric force of all the charges exerted by q is:

18. Plus two vector:

19. Exercise Consider three point charges located at the corners of a right triangle as shown in figure, where q1 = q3 = 5μC, q2 = -2μC, and a = 0,1m. Find resultant force exerted on q3. The resultant force exerted on q3 is: a q2 q3 a q1

20. Exercise Three point charges lie along the x axis. The positive charge q1 = 15μC is at x = 2m, the positive charge q2 = 6μC is at the origin, and the net force acting on q3 is zero. What is the x coordinate of q3. The x coordinate of q3 is: x = 2m O + x + q2 q1

21. 3 – The electric field Electric fields is the region of space around a charged object the source charge. When another charged obejct the test charge enters this electric field, an electric force acts on it.

22. The electric field vector at a point in space is defined as the electric force F acting on a positive test charge q0 placed at that point divided by the test charge:

23. P + * The electric field created by q is positive : If the source charge q positive, the situation with the test charge removed the source charge sets up an electric field at point P, directed away from q. The force is in the same direction as the field

25. P - < q 0 * The electric field created by q is negative: If q is negative , the force on the test charge is toward the sourse charge, so the electric field at P is directed toward the sourse charge. The force and the field are in opposite directions.

26. P + r : is the space from point P to the source charge q (m)

27. * The electric field at point due to a group of sourse charges can be expressed as the vetor sum: ri is the distance from the i th sourse charge qi to the point P (m). * The charge distribution is modeled as continuous, the total field at P in the lim it Δqi → 0 :

28. . If a charge q is unifromly distributed throughout a volume V, the volume charge densityρ is defined by: ρ = q/V (C/m3) . If a charge q is unifromly distributed throughout on a surface of area A, the surface charge densityσ is defined by: σ = q/A (C/m2) . If a charge q is unifromly distributed a long a line of length ℓ, the linear charge densityσ is defined by: ℓ = q/λ (C/m2)

29. . If the charge q is nonuniformly distributed over a volume, surface, or line, throughout a volume V, the of charge dq in a small volume, surface, or length element are:

30. Exercise In the air, there are a point electric charges Q = -3.10-6 C. Caculate the electric field at the point P to electric charge Q is 30cm ? The electric field at the point P to electric charge Q is 30cm:

31. P B + A - q1 q2 Exercise There are two point electric charges: q1 = -3.10-8C at A, q2 = 5.10-8C at B, for from AB = 10cm. At P, with PA = PB = 5cm. Find the electric field at the point P? r1 = r2 = 0,05m

32. - + Exercise: There are two point electric charges: q1 = 8µC at A, q2 = -6µC at B, for from AB = 10cm. At P, with PA = 8cm, PB = 6cm. Find the electric field at P ? P r1 r2 q2 A q1 B

33. Exercise A point charge of -4nC is located at (0, 1)m. What is the x component of the electric field due to the point charge at (4,-2)m?

34. Exercise 1. Put a point electric charge Q = - 5μC is at the origin. Caculate the electric field at point P located (4,-3)m? 2. There are two point electric charges: q1 = -10-8 C at A, q2 = 3.10 -8C at B, for from AB = 20cm. At point P is a centre of AB. Caculate : a. The electric field at point P. Draw a figure. b. The electric force affecting on electron put at P.

35. + + + + Exercise • Four charged particles are at the corners of a square of side a. Determine: • The total electric field at the centre of square. • The total electric force exerted on electron at the centre of square. 2q q 3q 4q

36. 4 – Electric field lines The electric field vector E is tangent to the electric field line at each point. The line has a direction, indicated by an arrowhead, that is the same as that of the electric vector.

37. B A The number of lines per unit area through a surface perpendicular to the lines is proportional to the magnitude of the electric field in the region. Thus, the field lines are close together where the electric field is strong and far apart where the field is weak. EA > EB

38. . The lines must begin on a positive charge and terminate on a negative charge. In the case of an excess of one type of charge, some lines will begin or end infinitely far away. The rules for drawing electric field lines are as follows: . The number of lines drawn leaving a positive charge or approaching a negative charge is proportional to the magnitude of the charge. . No two field lines can cross.

39. Electric field lines

43. Chapter 2GAUSS’S LAW

44. 1 – Electric Flux 2 – Gauss’s Law 3 – Application of Gauss’s Law to various charge distributions 4 – Conductors in electrostatic equilibrium

45. 1. Electric Flux ΦE (Vm) is proportional to the number of electric field lines that penetrate a surface.

46. θ dA 1. Electric FluxΦE (Vm) is proportional to the number of electric field lines that penetrate a surface. If the electric field is uniform and makes an angle θ with the normal to a surface of area A, the electric flux through the surface is: A is area (m2)

47. Exercise. In the electric field is uniform E = 4.10-5V/m has A = 20cm2 is area of suface and . Find the electric flux send to a area A.

48. Exercise. A flat surface of area 3,2m2 is rotated in a unifrom electric field of magnitude E = 6,2.105V/m. Determine the electric flux through this area :a. When the electric field is perpendicular to the surface.b. When the electric field is parallel to the surface.

49. 2. Gauss’s Law Electric flux ΦE through any closed gaussian surface is equal to the net charge qin inside the surface divided by ɛ0 :

50. Exercise. There are three point electric charges:q1 = -10-6C, q2 = 2.10-6C, q3 = 3.10-6C put inside the sphere, radius 30cm. Find the electric flux send to plane of sphere it. The electric flux send to plane of sphere is: