Static Electricity - Detailed Help

Assignment SE10: Electric Field

Objectives:
• The student should be able to define electric field and recognize the variables which effect (and do not effect) the electric field intensity at a given location.
• The student should be able to use electric field equations and relatively simple numbers to determine the magnitude and the direction of the electric field intensity at a given location.

The Physics Classroom - Static Electricity Unit, Lesson 4, Part a

 A charge Q creates an electric field. A test charge q is used to measure the strength of the electric field at a distance d from Q. The force F is experienced by the test charge q. The electric field strength at this location is given by the expression ___. List all that apply ... . Definition of Electric Field Strength: Any source of charge Q will create an electric field in the space surrounding it. The strength of an electric field (E) at any given location in this space can be determined by placing a test charge q in the space and measuring the force (F) which is exerted upon it. The electric field strength is defined as the amount of force per unit of charge on the test charge. E = F / q The electric field strength (E) is defined as the amount of force exerted upon a test charge per unit of charge on the test charge (q). That is, E = F / q. The electric force (F) depends upon a number of variables as described by Coulomb's law. Felect = k • Q1 • Q2 / d2 In the above equation, Q1 might be the source charge Q and Q2 might be the test charge q. If the expression for force as given by the Coulomb's law equation is substituted in for F in the electric field strength equation, then the equation for electric field becomes E = k • Q / d2

 A charge Q creates an electric field. A test charge q is used to measure the strength of the electric field at a distance d from Q. The electric field strength is defined as ____. Definition of Electric Field Strength: Any source of charge Q will create an electric field in the space surrounding it. The strength of an electric field (E) at any given location in this space can be determined by placing a test charge q in the space and measuring the force (F) which is exerted upon it. The electric field strength is defined as the amount of force per unit of charge on the test charge. E = F / q It is easy to become confused by the mathematics of electric field strength. It is important to bear in mind that there are always two charges involved in any electrical interaction. In this case, the charges are Q and q. Big Q represents the source charge which creates the electric field. Little q represents the test charge which is used to measure the strength of the electric field at a given location surrounding the source charge. Give considerable attention to the charge quantity - Q or q - being used in each equation.

 The standard metric unit on electric field strength is the ____. The electric field strength (E) at any location surrounding a source charge can be determined by measuring the force (F) exerted upon some test charge (q) which is placed at that location. E = F / q The standard metric units of a quantity can be understood by thinking about its formula. Electric field strength is the ratio of force to charge (see Formula Fix section above). So the units on electric field strength are units of force divided by units of charge. The standard metric unit of force is the Newton; the standard metric unit of charge is the Coulomb. So the standard metric unit of electric field strength is Newton/Coulomb, abbreviated N/C.

 A 4 microCoulomb charge exerts a force of 9.0 x 10^-6 Newton on a 3.0 x 10^-9 Coulomb test charge. The electric field strength created by the 4 microCoulomb charge is ____ N/C. Definition of Electric Field Strength: Any source of charge Q will create an electric field in the space surrounding it. The strength of an electric field (E) at any given location in this space can be determined by placing a test charge q in the space and measuring the force (F) which is exerted upon it. The electric field strength is defined as the amount of force per unit of charge on the test charge. E = F / q The electric field strength (E) is defined as the amount of force exerted upon a test charge per unit of charge on the test charge (q). That is, E = F / q. The electric force (F) depends upon a number of variables as described by Coulomb's law. Felect = k • Q1 • Q2 / d2 In the above equation, Q1 might be the source charge Q and Q2 might be the test charge q. If the expression for force as given by the Coulomb's law equation is substituted in for F in the electric field strength equation, then the equation for electric field becomes E = k • Q / d2 It is easy to become confused by the mathematics of electric field strength. It is important to bear in mind that there are always two charges involved in any electrical interaction. In this case, the charges are Q and q. Big Q represents the source charge which creates the electric field. Little q represents the test charge which is used to measure the strength of the electric field at a given location surrounding the source charge. Give considerable attention to the charge quantity - Q or q - being used in each equation.

 TRUE or FALSE: The quantity electric field is a vector quantity. (Note: Your actual True-False statement is picked at random from a collection of choices and may vary from the one listed here.) Electric Field as a Vector: The electric field at a given location about a source charge (Q) is a vector quantity. That is, it has a direction. The force upon a test charge (q) could be an attractive force (towards the source charge) or a repulsive force (away from the source charge) depending upon whether the Q and q are like-charged or oppositely charged. In defining the direction of the electric field, a convention is used so that the direction is always in the same direction regardless of the type of charge on q. According to the convention, the direction of the electric field is in the direction that a positive test charge would be pushed or pulled if placed in the space surrounding Q.

 By convention, the direction of the electric field is ____. Electric Field as a Vector: The electric field (E) at a given location about a source charge (Q) is a vector quantity. That is, it has a direction. The force upon a test charge (q) could be an attractive force (towards the source charge) or a repulsive force (away from the source charge) depending upon whether the Q and q are like-charged or oppositely charged. In defining the direction of the electric field, a convention is used so that the direction is dependent upon the type of charge on the source charge Q. According to the convention, the direction of the electric field is in the direction that a positive test charge would be pushed or pulled if placed in the space surrounding Q.

 A positive charge creates an electric field. The direction of the electric field would be ____. Electric Field as a Vector: The electric field (E) at a given location about a source charge (Q) is a vector quantity. That is, it has a direction. The force upon a test charge (q) could be an attractive force (towards the source charge) or a repulsive force (away from the source charge) depending upon whether the Q and q are like-charged or oppositely charged. In defining the direction of the electric field, a convention is used so that the direction is dependent upon the type of charge on the source charge Q. According to the convention, the direction of the electric field is in the direction that a positive test charge would be pushed or pulled if placed in the space surrounding Q. By convention, the direction of the electric field vector at any given location is the direction which a positive test charge would be pushed or pulled if placed at that location. Combining this convention with the rule that like charged objects repel, one can determine the direction of the electric field in the space surrounding a positive source charge. A positive source charge and a positive test charge will repel each other. That is, the positive test charge will be pushed away from the positive source charge at all locations in the space surrounding the source charge.

 A negative charge creates an electric field. The direction of the electric field would be ____. Electric Field as a Vector: The electric field (E) at a given location about a source charge (Q) is a vector quantity. That is, it has a direction. The force upon a test charge (q) could be an attractive force (towards the source charge) or a repulsive force (away from the source charge) depending upon whether the Q and q are like-charged or oppositely charged. In defining the direction of the electric field, a convention is used so that the direction is dependent upon the type of charge on the source charge Q. According to the convention, the direction of the electric field is in the direction that a positive test charge would be pushed or pulled if placed in the space surrounding Q. By convention, the direction of the electric field vector at any given location is the direction which a positive test charge would be pushed or pulled if placed at that location. Combining this convention with the rule that oppositely charged objects attract, one can determine the direction of the electric field in the space surrounding a negative source charge. A negative source charge and a positive test charge will attract each other. That is, the positive test charge will be pulled towards the negative source charge at all locations in the space surrounding the source charge.