摩擦力初中物理（Friction physics in junior high school）.doc

摩擦力初中物理（Friction physics in junior high school） 1. Two charges, charge conservation law and elementary charge (e = 1.60 x 10-19c) 2. Coulombs law F = KQ1Q2 / r2 (in a vacuum) * F = KQ1Q2 / epsilon r2 (in the medium) $Y: O7 {; _; C ~ ~ hF: the force of point charge (N) Its all right. K: static electricity constant K = 9.0 * 109N · m2 / C2, Q1, Q2: charge of 2 points (C) -s4 B) N7 p. X + T epsilon: dielectric constant r: the distance (m) of the distance between the two points (m) is in their line, the same charge repel each other, and the different charges attract each other. 3. Electric field intensity E = F/q (defined and calculated) E: electric field intensity (N/C) q: test charge of charge (C) is vector 4. The electric field of the vacuum point charge formation is KQ/r2 O L + U3 R: point to the location of the distance (m) (q! ~ (o % W ] 5 t ^ Q: the electric power of point charge 5. Electric field force F = qE , Y; V! ~ / ` * Y - pF: electric field force (N) q: what is the charge of electricity of electric field force (C) E: electric field intensity (N/C) 6. Electric potential and electric potential difference UA UAB = = epsilon A/q UA UB UAB = WAB/q = - Δ epsilon AB/q 7. The power of the electric field WAB = qUAB WAB: the work done by the electric field force of the charged body from A to B (J) q: the power (C) $g ? And E times w, d5 @ UAB: the electric potential difference between A and B in the electric field (V) (the field force is independent of the path) Epsilon A = qUA epsilon A: the electric potential energy of the charged body at point A (J) q: power (C) UA: the potential of A point (V) 9. The change of electric potential Δ epsilon AB = epsilon B - epsilon (charged body from place A to place B in the electric field of electric potential difference) The electric field force 10. Work with the potential to change Δ epsilon AB = - WAB = - qUAB (potential can increment is equal to the negative value of electric field forces work) 11. The capacitance C = Q/U