Electric Field

Electric Field and Lightning

• Lightning is a powerful natural phenomenon that occurs when there is a rapid release of energy due to the interaction of electric charges, resulting in an intense discharge of electricity.
• Lightning can be produced between opposite charges within a cloud, between separate clouds, and from a cloud to the ground
• Clouds become negatively charged and cause the ground to become positively charged, which then begins the discharge of lightning

Electric Field Basics

• An electric field is a region where an electric charge experiences a force
• Electric field is defined as the amount of electric force on a charged body that is exerted by external charged bodies
• Electric field is a way on how charges interact
• Field forces include electrostatic (Coulombic) and gravitational forces

Electric Field and Test Charges

• Two charged particles, A and B, will affect one another, resulting in repulsion if they share the same charge
• Point P will still experience force when particle B is removed because A always exerts its electric field
• The presence of an electric field around A can be proved by adding a test charge at position P

Electric Field and Electric Force

• A charged particle produces an electric field around itself, so another charged particle will react to it by experiencing electric force
• A charge produces an electric field in its surroundings, but this field cannot exert a net force on the charge that created it
• Electric field (E) at a point P is electric force (Fe) acting on a positive test charge (q0) placed at that point per unit charge
• Electric field is a vector quantity with an SI unit of newton per coulomb (N/C)
• Formula for electric field: E = Fe/q0
• Coulomb's law: Fe = k * |q1q2|/r^2
• Given q1 is the external charge q and q2 is the test charge q0 : Fe = k * |qq0|/r^2
• The electric field can be described as E = Fe/q0 = k * |q|/r^2
• The inverse-square law applies to the electric field equation

Electric Field Calculations

• The electric field is 1.505825 N/C at 4 m away from a 2.68 nC charge
• At a distance of 2120.14 m (approx. 2.12014 km) from a 2 mC charge, the electric field is 4 N/C
• For a 6 nC charged particle on the x-axis, the positions along the x-axis where the electric field is 3 N/C are x = ±4.24 m
• With a 2 nC charge at position (0, 4 m), the magnitude of the electric field at position (2 m, 0 m) is 0.9 N/C
• With a positive charge of 6 nC placed at (4 m, 0 m), the electric field at position (2 m, 2 m) is 6.74 N/C

Drawing Electric Field Lines

• Drawings involving positive charges should have rays directed away from the charge; negative charges should have them directed towards it
• Field lines should emanate from positive charge and terminate to negative charges
• Field lines should not intersect, only meet when there is an attractive force
• Density of lines shows the strength of the field; the more space between field lines, the weaker the electric field, equal spaces show a uniform field

Electric Field Key Points

• A charge produces an electric field around it, and a test charge reacts to it by experiencing electric force
• The electric field is a vector quantity and can be illustrated using electric field lines
• Formula for electric field: E = Fe/q0, where E is the electric field, Fe is the force and q0 is the test charge
• Electric field calculation: E = k * |q|/r^2, where E is the electric field, q is the charge that creates the electric field, r is the distance between q and the test charge, and k is the Coulomb constant (9 × 10^9 Nm²/C²)