University:
University of Cambridge
Course:
0625 IGCSE | Physics
Academic year:

2023
Views:

65

Pages:

2
Author:

Deddy A.

Chapter 15 Electric Forces & Fields Electric Charge Lightning is electrical in nature Existence of Positive and Negative Charges Conservation of Charge Like charges repel Unlike charges attract Lightning Rod Charge is quantized Sl units of charge: Coulomb (C) Qelectros-1.6 x 10-1 C Coulomb's Law fundamental F, like gravity An electric force has the following properties: 1. It is directed along a line joining the two particles and is inversely propor tional to the square of the separation distance r, between them. 2. It is proportional to the product of the magnitudes of the charges, [qil and 192, of the two particles. 3. It is attractive if the charges are of opposite sign and repulsive if the charges have the same sign. FE = ke 91 92 2 k, is Coulomb's constant: k = 8.988 x 10° N m2/C2 ★v similar to Newton's Law of Gravity: Newton's law of gravity FGGN my m 2 GN = 6.67 x 10-11 N m2/kg2 - electric force can be attractive/repulsive, but gravity is ONLY attractive. g is x36 orders of mag. weaker than electricity. Insulators & Conductors Conductors emove freely in response to an electric force semi-conductors eg, silicon ↳ metals - insulators all other materials. (can polarize inside atom) ↳ glass, rubber Charges with the same sign repel each other. F Charges with opposite siges attract each other. Superposition Principle the electric force & one point due to multiple electric charges is the vector sum of the forces exerted by each charge. F Electric Field poine R The electric field represents the force on a charged object placed anywhere (r) in space. Electric field: E(r): Vector quantity The electric field E produced by a charge q at the location of a small "test" charge q, is defined as the electric force F exerted by q on go divided by the test charge q. It is the force on a unit charge placed at prodnad by charge Q (NIC) E= FE 10-test charge Magnitude of the electric field caused by a point charge q. E= E The direction of the field is the direction of the force that acts on a positive test charge. More, the slettric fa If y is negative, the electric field at Ppoons radially immards toward = 4, smaller object w/ (4) charge 2