Repetition of basic of electrostatics: Movement of electric charge in an electric field NGOC HOANG ANH THAN GROUP 6 Electric charge • Electric charge is the physical property of matter which cause matter to experience an electric force. Positive and negative electric charges are the two types of charges • Electric charge can be calculated by: Q=I×t where: Q = Electric Charge (Coulomb) I = Electric Current (Ampere) t = Time (second) Coulomb’s Law • Coulomb's law states that the electrical force between two charged objects is directly proportional to the product of the quantity of charge on the objects and inversely proportional to the square of the separation distance between the two objects. • In equation form, Coulomb's law can be stated as k x Q1 x Q2 F= r2 • Where Q1: the quantity of charge on object 1 (in Coulombs) Q2: the quantity of charge on object 2 (in Coulombs) r: the distance of separation between the two objects (in meters). k: a proportionality constant known as the Coulomb's law constant. Electric field • Electric field is the area in which a charge experiences attreactive or repulsive force around it • The electric field around a positive charge will attract negative charge and repel positive charge. While a negative charge will attract positive charge and repel negative charge. Electric field • The direction of the electric field is outwards the positive charge and towards the negative charge Electric field • Electric field is defined as the electric force per unit change and can be calculated by: 𝑬= 𝑭 𝑸 where: E = electric field strength (Newton/Coulomb) F = electric force (Newton) Q = electric Charge (Coulomb) Movement of electric charge in an electric field A charged particle in an electric field experiences a force, and if it is free to move, an acceleration. If the only force is due to the electric field, then F ma qE. When q is positive, the force experienced is parallel to E. When q is negative, the force experienced is opposite to E as shown in the figure below. Movement of electric charge in an electric field • And when a new particle enter the electric field, it will go in a parabol dicrection toward positive charge plate or negative charge plate due to its charge, because it is affected by the force in electric field. --- --- -- - + + + + + + + ++ Movement of electric charge in an electric field Proof. From the equations of motion of a particle, the velocity and displacement relations are If initially the particle is at rest, then 𝑢 = 0. Then the equations become Movement of electric charge in an electric field When the particle projection is perpendicular to the direction of the electric field, then motion is in the upward direction (along the y-axis). So, x Now, t= , where x is the distance travelled by the particle under the influence of electric v field and v is the drift velocity attained. Eliminating the time t in the above equation, we get, So, we see that the y-x relation is actually a parabola. Therefore, the particle follows a parabolic trajectory. Movement of electric charge in an electric field We see that the y-x relation is actually a parabola. Therefore, the particle follows a parabolic trajectory.
