AP Physics 2 : Electric Force in an Electric Field
Study concepts, example questions & explanations for AP Physics 2
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Example Questions
Example Question #1 : Electric Force In An Electric Field
There is a uniform electric field of 
We will use the following equation:
Plug in known values.
Since the particle is negatively charged, it will move opposite the electric field lines (south).
Example Question #1 : Electric Force In An Electric Field
In the lab, you have an electric field with a strength of 
The equation for force on a charge within an electric field is:
Plug in known values and solve.
Example Question #1 : Electric Force In An Electric Field
There are two point charges in a vacuum, 
There is no force felt by the charges
The equation for force given two charges is:
We're given both charges, and we know the distance between them, and we know the Coulomb's constant, so we plug in known values.
Because the answer is negative, the force experienced is attractive, which is what we expect from oppositely charged particles.
Example Question #1 : Electric Force In An Electric Field
In a region of space there is an electric field. The field is directed straight down and has a field strength of 
The electron experiences no force in this region of space
Since it's an electric field, the velocity does not matter, only the charge.
Since the electron carries a negative charge, it accelerates opposite to the field, which is straight up.
Example Question #1 : Electric Force In An Electric Field
An electric dipole, with its positive charge above the negative charge, is in a uniform electric field that points to the right, as diagrammed above. What is the net torque and the net force on the dipole in this electric field?
Net torque = zero
Net force = right
Net torque = counterclockwise
Net force = zero
Net torque = clockwise
Net force = zero
Net torque = counterclockwise
Net force = left
Net torque = zero
Net force = zero
Net torque = clockwise
Net force = zero
Since the net charge of the dipole is zero, the net force will also be zero since 
Example Question #6 : Electric Force In An Electric Field
In a region of space, there is a uniform electric field whose magnitude is 
Like all forces, electrostatic forces are vectors and must be added using a vector diagram. Fortunately, we can calculate each force separately, then combine them on the vector diagram. For the force due to the field,
This force is directed to the left since negatively charged particles experience force opposite the direction of the field.
For the force due to the charge at the origin:
This force is directed down, towards the particle at the origin because opposites attract. Now we draw the vectors:
The dashed line represents the sum. Use the Pythagorean theorem to find the vector sum.
Example Question #1 : Electric Force In An Electric Field
Assume that the uniform electric field has a magnitude of 
Use the formula to find the force that the test charge experiences.
Substitute the values and determine the force.
Example Question #1 : Electric Force In An Electric Field
A test charge of 
Determine the force on the charge.
None of these
The definition of electric force on a charge in an electric field:
Plug in values.
Example Question #9 : Electric Force In An Electric Field
A test charge of 
Determine the force on the charge.
None of these
The definition of electric force on a charge in an electric field:
Plug in values.
Example Question #1 : Electric Force In An Electric Field
A test charge of 
Determine the force on the charge.
None of these
The definition of electric force on a charge in an electric field:
Plug in values.
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