Electromagnetism I Week 8

Contents Overview Overview Coulomb’s Law Coulomb’s Law Current Current Voltage Voltage Resistance Resistance Energy and Power Energy and Power Review Review

The Four Forces 1. Strong 2. Electromagnetic 3. Weak 4. Gravity

James Clerk Maxwell First person to fully formulate the classical laws of electricity and magnetism. First person to fully formulate the classical laws of electricity and magnetism.

Maxwell’s Equations of Classical Electrodynamics

Electrostatics The study of electric forces when all charges are at rest. The study of electric forces when all charges are at rest. Every particle has a property called chargem. The charge is either positive, or negative, or zero. Every particle has a property called chargem. The charge is either positive, or negative, or zero. Charge is always conserved. Charge is always conserved. Measured on Coulombs. Measured on Coulombs.

Coulomb’s Law F1 = kqQ/r 2 F1 = kqQ/r 2 F1 = - F2 F1 = - F2 k = 1/4πε 0 k = 1/4πε 0 It is “sign sensitive”. It is “sign sensitive”. Very similar to gravitation. Very similar to gravitation. +Q +q F1 F2

The Electric Field +q-q

Electric Field Lines

Definitions Current: i = q/t Current: i = q/t Voltage: V = E/q Voltage: V = E/q Power: P = q/t = Vi Power: P = q/t = Vi Energy: E = Pt = Vit Energy: E = Pt = Vit

Current I = q/t I = q/t j = I/a = q/at j = I/a = q/at Amperes Amperes q t

Current vs. EF +Q-Q

Current 3A 2A 1A

Voltage V = E/q V = E/q Also called electric potential Also called electric potential Volts Volts

Voltage 3V

Resistance R = V/i R = V/i Ohms, Ω. Ohms, Ω.

Energy and Power i = q/t i = q/t V = E/q V = E/q R = V/i R = V/i E = Vit E = Vit P = E/t = Vi P = E/t = Vi

Electric Circuits Series Series Parallel Parallel

Current Series Series Parallel Parallel I = I1 = I2 = I3I = I1 + I2 + I3

Voltage Series Series Parallel Parallel V = V1 + V2 + V3V = V1 = V2 = V3

Resistance Series Series I = I1 = I2 = I3 V = V1 + V2 + V3 V/I = V1/I + V2/I + V3/I V/I = V1/I1 + V2/I2 + V3/I3 R = R1 + R2 + R3 Parallel Parallel I = I1 + I2 + I3 V = V1 = V2 = V3 I/V = I1/V + I2/V + I3/V I/V = I1/V1 + I2/V2 + I3/V3 1/R = 1/R1 + 1/R2 + 1/R3

Review Coulomb’s Law F = kQq/r2 F = kQq/r2Definitions i = q/t i = q/t V = E/q V = E/q P = q/t = Vi P = q/t = Vi E = Pt = Vit E = Pt = Vit Electric Circuits Series Series I = I1 = I2 = I3 V = V1 + V2 + V3 R = R1 + R2 + R3 Parallel Parallel I = I1 + I2 + I3 V = V1 = V2 = V3 1/R = 1/R1 + 1/R2 + 1/R3

Next Week Magnetism Magnetism