Physics 133 electromagnetism Electric Field MARLON FLORES SACEDON

Electric Fields + What is electric field? An electric field is a vector field that associates to each point in space the Coulomb force experienced by a unit electric charge. Electric field is defined as the electric force per unit charge. The direction of the field is taken to be the direction of the force it would exert on a positive test charge. The electric field is radially outward from a positive charge and radially in toward a negative point charge. +𝑞 +𝑞 +𝑞 +𝑞 +

Electric Fields What is electric field? An electric field is a vector field that associates to each point in space the Coulomb force experienced by a unit electric charge. Electric fields converge and diverge at electric charges and they can be induced by time-varying magnetic fields. The electric field combines with the magnetic field to form the electromagnetic field.

Electric Fields Electric field lines

Electric Fields - + 𝐸= 1 4𝜋 𝜖 𝑜 ∙ 𝑄 𝑟 2 𝐸= 𝐹 𝑞 𝐹=𝑞𝐸 𝐸= 𝑘 𝑄𝑞 𝑟 2 𝑞 +𝑞 𝐹=𝑞𝐸 𝑟 𝐸 𝐹 𝐸 𝐹 Definition of Electric field +𝑞 𝑟 𝐸= 𝑘 𝑄𝑞 𝑟 2 𝑞 - 𝑄 + 𝑄 Problem: A point charge 𝑞=−8.0 𝑛𝐶 is located at the origin. Find the electric field vector at the field 𝑥=1.2𝑚, 𝑦=−1.6 𝑚. 𝐸= 1 4𝜋 𝜖 𝑜 ∙ 𝑄 𝑟 2 𝐸=𝑘 𝑄 𝑟 2 or +𝑥 −𝑦 _ 𝑞=−8.0 𝑛𝐶 𝑟= 1.2 2 + 1.6 2 =2𝑚 1.2𝑚 1.6 𝑚 Where: 𝐸 = electric field 𝑁 𝐶 , vector quantity 𝑘 = 9𝑥 10 9 𝑁. 𝑚 2 𝐶 2 𝑄 = source charge 𝐶 +𝑞 = unit charge 𝐶 𝐸=9𝑥 10 9 𝑁. 𝑚 2 𝐶 2 −8.0 𝑛𝐶 2𝑚 2 𝑟 𝐸=9𝑥 10 9 𝑁. 𝑚 2 𝐶 2 −8.0 𝑥 10 −9 𝐶 2𝑚 2 +𝑞 𝐸=18 𝑁 𝐶 towards 𝑄 ANSWER

Electric Fields - - + 𝐸= 1 4𝜋 𝜖 𝑜 ∙ 𝑄 𝑟 2 Superposition of electric field - 𝑄 3 𝑟 3 𝐸= 1 4𝜋 𝜖 𝑜 ∙ 𝑄 𝑟 2 - 𝑄 2 𝐸=𝑘 𝑄 𝑟 2 or 𝑟 2 𝐸 3 Where: 𝐸 = electric field 𝑁 𝐶 , vector quantity 𝑘 = 9𝑥 10 9 𝑁. 𝑚 2 𝐶 2 𝑄 = source charge 𝐶 +𝑞 = unit charge 𝐶 𝐸 2 𝐸 1 + 𝑄 1 +𝑞 𝑟 1 𝐸 = 𝐸 1 + 𝐸 2 + 𝐸 3 +… Vector sum or Geometric sum

Electric Fields Problems 1. A charge of 30 𝑠𝑡𝑎𝑡𝐶 and another charge of 50 𝑠𝑡𝑎𝑡𝐶 are 10𝑐𝑚 apart. What is the field intensity at a point (a) 8𝑐𝑚 from the30 𝑠𝑡𝑎𝑡𝐶, (b) 5cm from the 30 𝑠𝑡𝑎𝑡𝐶 , and (c) 6𝑐𝑚 from the 30 𝑠𝑡𝑎𝑡𝐶 ? 2. At the three consecutive corners of a square 10 cm on the side are point charges of 50𝑥 10 −9 𝐶; 100𝑥 10 −9 𝐶; 100𝑥 10 −9 𝐶 respectively. Find the electrostatic field at the fourth corner of the square.

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