PHY B1 SEM 2

• Electrical charge is the basic interaction between particles in any type of material.
• There are two kinds of electric charges: Positive charge (+VE) and Negative charge (-VE).
• A charged body is due to two fundamental particles – electron & proton.
• An electron carries a negative charge, e, which has a value of: e = -1.6x10^-19 C.
• A proton carries a positive charge, p, which has a value of: p = +1.6 X 10^-19 C.
• The unit for charge is Coulomb (C).
• Charges of the same sign (like chargers) repel one another.
• Charges of the opposite sign (unlike chargers) attract one another.
• A neutral object is an object that carries equal amount of positive and negative charges.
• A negatively charged object is produced when a neutral object gains some extra electrons.
• A positively charged object is produced when a neutral object loses some electrons or has some excess protons.
• These phenomena happen according to the law of conservation of charges which states: Charge cannot be created nor destroyed, it can only be transferred from one material to another.
• The charge of an object is always a multiple of e, where e = ±1.6x10^-19 C.
• Coulomb’s Law states that the electric force, F between two charges separated by a distance, r, is inversely proportional to the square of the separation, r between the two charges, and directly proportional to the product of the magnitudes of the charges, Q1 and Q2.
• Coulomb’s Law can be written as: F = kQ1Q2/r², where k = Coulomb constant which has the value of 9 X 10^9 N m2 C-2.
• An electric field, E, is a region where an electric force acts on a charge when placed in the region
• Electric field is defined as the electric force acting per unit charge, with E being a vector quantity and the unit being N C^-1
• Electric field patterns can be represented by electric field lines, which point in the direction of the E vector at any point
• Electric field lines do not intersect each other, and the number of lines per unit area determines the strength of the electric field
• The strength of the electric field is large when field lines are close together and small when they are far apart
• A positive and a negative charge can produce an electric field
• For a positive point charge, the direction of the electric field is outward from the charge in all directions (3 dimensions)
• For a negative point charge, the direction of the electric field is toward the charge in all directions (3 dimensions)
• The strength of the electric field decreases as the distance from the charge increases
• Electric field strength, E, can be expressed in terms of k, Q, and r
• According to Coulomb’s Law, E is inversely proportional to r^2
• FLUX = Amount of Electric field, E lines passing through a surface area, A
• The density of the lines is proportional to the density of The Electric flux.

  Electric flux can be defined as the number of lines passing through a given surface area.
• Surface area increase, flux increase
• Electric field increase, flux increase
• If a loop of area, A is placed within an Electric Field with the plane of the loop perpendicular to the electric field then the electric flux through the loop is phi(E) = E A
• phi(E) = E A , E is electric field, A is surface area, unit is Volt metres (V m) or (N m² C-1)
• If the E field is not perpendicular to the plane of an area, phi (E) = E A cos0
• Electric field is region in which an electric force will act on a charge when the charge is placed in the region.
• Electric field strength is measure of the strength of an electric field at a given point in space, equal to the force the field would induce on a unit electric charge at that point.