Physics Notes - Electric Field PDF

# Chapter Flectric Field ## Introduction * Electric charge *q* * +ve Charge Ex: Protons & +ve ions * -ve charge Ex: electrons & -ve ions * Charges Can't be Created, it already exists in isolated Systems. ## Properties of electric charges 1. ***Quantized:*** Because charges are exist in i...

# Chapter Flectric Field ## Introduction * Electric charge *q* * +ve Charge Ex: Protons & +ve ions * -ve charge Ex: electrons & -ve ions * Charges Can't be Created, it already exists in isolated Systems. ## Properties of electric charges 1. ***Quantized:*** Because charges are exist in integer multiples of electron charge $q = \pm Ne$ * q = charge * N = integer * e = electron charge * electron charge = -e * Proton charge = +e 2. ***Conservation:*** * If a reaction involves charged particles. * The total charge before and after the reaction are the Same. * No reaction that creates or destroys any electric charge ## Materials * **conductors:** (rich of electrons) * like Cu * Fe * **Semiconductors:** * between * like Si * Ge * **Insolators:** (Poor of electrons) ## Charging by:- 1. ***Conduction:*** * Require contact between the object and the charge * Produce the Same charge 2. ***Induction:*** * Require No contact between the object and the charge * Produce the opposite charge ## Coulomb's Law * Measure the Force *F* between 2 point charges * Point charge: refers to a particle of Zero Size carries an electric charge. * Coulomb's Law states that: *F12* the electric force between 2 point charges directed along the line joining 2 point charges. * $F \propto \frac{q_1q_2}{r^2}$ * $F = K_e\frac{|q_1q_2|}{r^2}$ $N$ Newtons. * $K_e$ Constant: * $K_e = \frac{1}{4\pi\epsilon_o}$ = $8.99 \times 10^9 \frac{Nm^2}{C^2}$ * $\epsilon_o$ : Permittivity of free space = $8.85 \times 10^{-12} \frac{C^2}{Nm^2}$. ## Resolution * Components of a vector * The Vector *A* can be represented by $A = A_x i + A_y j$ * Where: * *i*: is a unit vector in *x* direction * *j*: is a unit vector in *y* direction * *k*: is a unit vector in *z* direction * *A_x, A_y*: are the components of the vector in *x, y* respectively. * $A_x$ = *A* cos θ * $A_y$ = *A* sin θ * $A = \sqrt{A_x^2 + A_y^2}$ (magnitude) * θ = $tan^{-1}\frac{A_y}{A_x}$ (direction) ## Super Position * Similar charges: repulsion force * Opposite charges: attraction force * If there are more than two charges, the net force on the charge is the Vector Sum of all forces on this charge. * $F = F_1 + F_2 + F_3 .... $ * $\sum Fx = F_1 cos θ + F_2 cos φ$ * $F y = F_1 sin θ + F_2 sin φ$ * magnitude = |F| = $√(F_x ^ 2 + F_y ^ 2 )$ * direction = φ = $tan^{-1}\frac{F_y}{F_x}$. * Total Force using resolution of vectors * $F_x = F_1 cos θ + F_2 cos φ$ * $F_y = F_1 sin θ - F_2 sin φ$ * magnitude = $√(F_x ^ 2 + F_y ^ 2 )$ * direction = θ = $tan^{-1} \frac{F_y}{F_x}$ | Prefix | Symbol | Value | |---|---|---| | Tera | T | 10¹² | | Giga | G | 10⁹ | | Mega | M | 10⁶ | | Kilo | K | 10³ | | milli | m | 10⁻³ | | micro | µ | 10⁻⁶ | | nano | n | 10⁻⁹ | | pico | p | 10⁻¹² |