# Electric field and lines and their Different properties.

Electric field and lines and their Different properties.

Electric Field:- The space around a charge, up to which its inti can be experienced is called the electric field of that charge. The electric field of a charge is the space property by virtue of which the charge modifies the space ar itself. Due to the electric field of a charge, any other ch experiences the force. If a test charge of very small m point in the electric field, then an electrostatic for an st charge of very small magnitude is held at an eld, then an electrostatic force starts The magnitude of this force is different at rent points in the field, also the direction of force at various points in an electric field are different. The ic field intensity is measured as the force acting on a unit positive charge placed at any point in the field (Test charge is that charge which cannot affect the intensity of the electric field at the point where it is placed, that is why the magnitude of test charge must be vanishingly small). Electric field intensity: The electric field intensity or the strength of the electric field at a point due to a source charge is defined as the electrostatic force per unit positive charge acting on a small test charge of absolute magnitude zero) placed at that point without disturbing the source charge. Consider a positive test charge q experiencing a force F. (due to q) when placed at the observation point  Then +F electric field at the observation point is given by E = 90 In the above expression, for the electric field, it is assumed that when the test charge q is placed at the observation point, it does not disturb the source charge. One way to guarantee that test charge q does not disturb the source charge is to keep its magnitude vanishingly small. If the test charge q is not small, it will disturb

 Electric field and lines and their Different properties.
the source charge and hence the electric field at the observation point will be different from the one, the source charge remained in its original position. Hence the expression for the electric field will now become In the eqn limit g, → 0 is written. It implies that the value of q must be as small as possible. So that it can not disturb the source charge. The value of q, may not be zero through its value may be equal to From eqn. the magnitude of the intensity of the electric field can be expressed as follows Thus, “The intensity of the electric field at a point is defined as the ratio of force exerted by the source charge on a test charge placed at that point, to the magnitude of the test charge." Unit of the intensity of the electric field: As we have discussed earlier that intensity of the electric field

The physical significance of electric field intensity : If a point charge g is placed in an electric field of intensity E, then the force acting on it will be F=qE In scalar form it can be written as: F=qE Hence, if the intensity of the electric field at a point is to be determined, then using eqn. (1) the direction and the magnitude of the force acting on a charge placed at that the point can be obtained. This is the physical significance of the intensity of the electric field.

The intensity of Electric Field Due to a Point Charge Lets us consider a point charge +ÄŸ placed in air or vacuum at point ‘O'. At 'r' distance apart from this point, a point P is taken at which the intensity of The electric field due to charge +q is to be determined. Suppose a test charge +q, is placed at point P, then the force between these two charges can be given by Coulomb's law.

The electric field due to a charge q is present at each point of three-dimensional space The magnitude of the field decreases with an increase in distance from the charge The direction of electric field intensity due to a positive charge is always radially outwards. the expansion of the electric field due to positive charge +g is shown in the two-dimensional plane.

Electric Lines of Force or Field Lines:-

If a positive charge which is free to move is placed in an electric field, then it experiences an electrostatic force and it will move in the direction of the force. If the direction of force changes continuously, then the direction of the motion of charge will also change the charge will move along a curved path. The path followed by force, the positive charge in an electric field is called the electric line of force or field line. The concept of electric lines of force was first introduced by Michael Faraday.

the electric lines of force of a positively charged sphere are shown. If a free unit the positive charge is placed near the positively charged sphere, then due to repulsion it will move away from sphere and will go to infinity. Hence, the lines of force due to an isolated positive a charge is radially outward i.e., the lines of force due to positive charge starts from the charge and goes to infinity. the electric lines of force due to a negatively charged sphere is shown. When a free unit the positive charge is placed in the electric field of a negatively charged sphere, then due to attraction force it will move towards the negative charge from infinity. Hence, the lines of force due to an isolated negative charge are radially inwards i.e., the lines of force due to negative charge starts from infinity and ends at a negative charge. it is clear that in the electric field of a charged sphere the lines of force are straight and radial. Either they appear to start from the center of the sphere or end at the center of the sphere. Therefore, the charge is given to a spherical conductor is considered to be concentrated at its center.

“An electric line of force or field line is that the imaginary smooth curve in an electric field along
which a unit positive actually tries to move if it is free to do so.”Electric lines of force may be a straight line or curved line. The tangent drawn at any point of the curve gives the direction of the electric field. the electric lines of force in various types of the electric field are shown.

Cedric lines of force.

The lines of force for the system o two equal and opposite charges are the lines of force due to two equal and like charges. We find that the lines of force from the two charges tend to oppose each other and at distant points, the lines of force become approximately partial This implies that electric lines of force starting from a system of two equal and similar charges exert side-ways pressure on each other. This explains the repel- sion between two similar charges. Moreover, there lies a point N in the midway between two charges, where the resultant electric field is zero, hence N is called Neu- try point. If two positive charges are equal in magnitude, then the neutral point is situated at the mid-point of the lines joining the two charges. But if the charges are not equal m magnitude, then the neutral point is situated on the line joining the two charges but near the charge whose magnitude is smaller the lines of force due to a positively charges sheet.

Properties of electric lines of force: Electric lines.

Electric lines of forces start from positive charge and end into the negative charge or on a conductor, Tangent is drawn at any point gives the direction of electric field intensity at that point Thus, property gives the reason why two lines of force never intersect It is because if two lines intersect at any point then two tangents can be drawn at that point means there may be two directions of electric field intensity which is not possible., Lines of forces try to contract longitudinally or a tension acts lengthwise. This property can explain why two, unlike charges, pull each other, The lines of force have a tendency to separate from each in the direction perpendicular to their length. This property gives the reason why the line always leaves or meets the surface normally. The electric field intensity at any point in the electric field is measured by the number of lines crossing per unit area around that point, the area being held normal to the field lines. In other words, we can say that if the lines of force are closer, then the electric field is stronger, whereas in the region where the lines of force are separated, the field is weaker, The electric lines of force do not pass through a conductor. This shows that electric field inside a con- the doctor is zero, Electric lines of forces start normally from a positively charged conductor and end normally on the surface of a negatively charged conductor, N.

Uniform and non-uniform electric field:-

When electric field intensity is equal in magnitude and in direction at every point is called a uniform electric field. Otherwise, it is called a non-uniform electric field. In the uniform electric field, the lines of force are parallel to each other and equidistant. These fields are shown by a parallel and non-parallel set of lines respectively Uniform and non-uniform electric field: When electric field intensity is equal in magnitude and in direction at every point is called a uniform electric field. Otherwise, it is called a non-uniform electric field. In the uniform electric field, the lines of force are parallel to each other and equidistant. These fields are shown by parallel and non-parallel set of lines respectively. the uniform and non-uniform electric fields.