electric field
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What is an electric field?
An electric field is an electric property linked to each point in space where charge exists. It can be understood as the force per unit positive charge that would be exerted before the field is disturbed.
The strength of an electric field (E) at any location is the electric force (F) exerted per unit positive electric charge (q) at that point, or simply (E = F/q). Electric fields are generated by electric charges and changing magnetic fields.
Electric fields are represented by field lines, which start on positive charges and end on negative charges. The direction of the force on a positive charge is arbitrarily chosen as the direction of the electric field. The field is stronger where the lines are close together.
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How does an electric charge create an electric field?
An electric charge creates an electric field, which is an electric property associated with each point in space when charge is present in any form. Instead of a direct interaction between two charges, one charge creates an electric field that extends outward, and the force exerted on a second charge is a direct interaction between the electric field and the second charge.
The electric field from a charge is directed away from the charge when the charge is positive and toward the charge when it is negative. The magnitude of the electric field depends on the source charge and is directly proportional to the amount of charge. The electric field is an important concept because it determines the force that would be exerted on a unit charge at that position in space.
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In which direction does an electric field point around a positive and a negative charge?
An electric field is an electric property associated with each point in space where charge is present in any form. Electric fields are represented by field lines, which depict the field's direction. The direction of the force on a positive charge is arbitrarily chosen as the direction of the electric field.
The electric field around an isolated positive charge is oriented radially outward because positive charges repel each other. For a negative charge, the field is oriented radially inward, as the force on a positive charge would be toward the negative charge.
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What does electric field strength mean and how can it be measured?
The electric field is an electrical property that exists at every point in space where there is an electric charge. Electric field strength, also called electric field intensity, is the value of E that expresses the magnitude and direction of the electric field.
The strength of an electric field E at any point in space is defined as the electric force F exerted per unit positive electric charge q at that point, or E = F/q. The units for the electric field are newtons per coulomb or volts per meter.
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What do electric field lines represent and how are they drawn around multiple charges?
Electric field lines represent the path a positive electric charge would follow if it were free to move within an electric field. These lines indicate the field's direction at any given point, with the density of the lines showing the field's magnitude.
When drawing field lines around multiple charges, the lines begin on positive charges and end on negative charges. The number of lines emerging from or terminating on a charge is proportional to the magnitude of the charge. The resulting field is the vector sum of the individual fields, and the lines are continuous everywhere except at the charges themselves.
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How are electric fields used in real-life technology and devices?
Electric fields are fundamental to many technologies. They exert force on charged objects, which is how electric fields are used to control electron movement in electron tubes. They also appear in electric clocks, traffic lights, radio and television sets, and automobile starter motors.
The magnitude of an electric field at a point in space equals the force exerted on a unit charge at that position and is measured in newtons per coulomb, or volts per meter. Electric fields also relate to voltage, as the difference in potential between two points measures how strongly charges are influenced to move.
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electric field, an electric property associated with each point in space when charge is present in any form. The magnitude and direction of the electric field are expressed by the value of E, called electric field strength or electric field intensity or simply the electric field. Knowledge of the value of the electric field at a point, without any specific knowledge of what produced the field, is all that is needed to determine what will happen to electric charges close to that particular point.
Instead of considering the electric force as a direct interaction of two electric charges at a distance from each other, one charge is considered the source of an electric field that extends outward into the surrounding space, and the force exerted on a second charge in this space is considered as a direct interaction between the electric field and the second charge. The strength of an electric field E at any point may be defined as the electric, or Coulomb, force F exerted per unit positive electric charge q at that point, or simply E = F/q. If the second, or test, charge is twice as great, the resultant force is doubled; but their quotient, the measure of the electric field E, remains the same at any given point. The strength of the electric field depends on the source charge, not on the test charge. Strictly speaking, the introduction of a small test charge, which itself has an electric field, slightly modifies the existing field. The electric field may be thought of as the force per unit positive charge that would be exerted before the field is disturbed by the presence of the test charge.
The direction of the force that is exerted on a negative charge is opposite that which is exerted on a positive charge. Because an electric field has both magnitude and direction, the direction of the force on a positive charge is chosen arbitrarily as the direction of the electric field. Because positive charges repel each other, the electric field around an isolated positive charge is oriented radially outward. When they are represented by lines of force, or field lines, electric fields are depicted as starting on positive charges and terminating on negative charges. A line tangent to a field line indicates the direction of the electric field at that point. Where the field lines are close together, the electric field is stronger than where they are farther apart. The magnitude of the electric field around an electric charge, considered as source of the electric field, depends on how the charge is distributed in space. For a charge concentrated nearly at a point, the electric field is directly proportional to the amount of charge; it is inversely proportional to the square of the distance radially away from the centre of the source charge and depends also upon the nature of the medium. The presence of a material medium always diminishes the electric field below the value it has in a vacuum.
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At times the electric field itself may become detached from the source charge and form closed loops, as in the case of charges accelerating up and down the transmitting antenna of a television station. The electric field with an accompanying magnetic field is propagated through space as a radiated wave at the same speed as that of light. Such electromagnetic waves indicate that electric fields are generated not only from electric charges but also from changing magnetic fields.
The value of the electric field has dimensions of force per unit charge. In the metre-kilogram-second and SI systems, the appropriate units are newtons per coulomb, equivalent to volts per metre. In the centimetre-gram-second system, the electric field is expressed in units of dynes per electrostatic unit (esu), equivalent to statvolts per centimetre.