Electric Force in an Electric Field - AP Physics 2
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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?
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?
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Since the net charge of the dipole is zero, the net force will also be zero since 
. The force on the positive charge on top will be directed to the right since positive charge experiences force in the direction of the electric field. For the negative charge on the bottom, the force will be to the left. Both of the forces contribute to a clockwise torque.
Since the net charge of the dipole is zero, the net force will also be zero since
There is a uniform electric field of 
pointing north. What force will a particle of 
experience?
There is a uniform electric field of
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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).
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).
There are two point charges in a vacuum, 
and 
, kept 
from each other. What is the force experienced by the charges?
There are two point charges in a vacuum,
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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.
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.
In the lab, you have an electric field with a strength of 
. If the force on a particle with an unknown charge is 
, what is the value of the charge on this particle?
In the lab, you have an electric field with a strength of
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The equation for force on a charge within an electric field is:
Plug in known values and solve.
The equation for force on a charge within an electric field is:
Plug in known values and solve.
Assume that the uniform electric field has a magnitude of 
, which points in the positive x-direction. What is the force magnitude this field exerts on a 
charge?
Assume that the uniform electric field has a magnitude of
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Use the formula to find the force that the test charge experiences.
Substitute the values and determine the force.
Use the formula to find the force that the test charge experiences.
Substitute the values and determine the force.
In a region of space there is an electric field. The field is directed straight down and has a field strength of 
. Into this region of space, an electron is moving north with a velocity of 
. What will the electron's acceleration be in this region of space? Include both magnitude and direction.
In a region of space there is an electric field. The field is directed straight down and has a field strength of
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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.
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.
In a region of space, there is a uniform electric field whose magnitude is 
directed to the right as diagrammed above. There are two charged particles in the field: a positive particle at the origin with charge 
and another at point (0,2) meters with charge 
as shown. What is the net force on the 
particle located at (0,2) meters?
In a region of space, there is a uniform electric field whose magnitude is
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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.
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.
A test charge of 
is placed in an electric field of 
.
Determine the force on the charge.
A test charge of
Determine the force on the charge.
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The definition of electric force on a charge in an electric field:
Plug in values.
The definition of electric force on a charge in an electric field:
Plug in values.
A test charge of 
is placed in an electric field of 
.
Determine the force on the charge.
A test charge of
Determine the force on the charge.
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The definition of electric force on a charge in an electric field:
Plug in values.
The definition of electric force on a charge in an electric field:
Plug in values.
A test charge of 
is placed in an electric field of 
. Determine the force on the charge.
A test charge of
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The definition of electric force on a charge in an electric field is:
The definition of electric force on a charge in an electric field is:
A test charge of 
is placed in an electric field of 
. Determine the force on the charge.
A test charge of
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The definition of electric force on a charge in an electric field is:
The definition of electric force on a charge in an electric field is:
A test charge of 
is placed in an electric field of 
. Determine the force on the charge.
A test charge of
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The definition of electric force on a charge in an electric field is:
The definition of electric force on a charge in an electric field is:
A test charge of 
is placed in an electric field of 
.
Determine the force on the charge.
A test charge of
Determine the force on the charge.
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The definition of electric force on a charge in an electric field:
Plug in values.
The definition of electric force on a charge in an electric field:
Plug in values.
Calculate the force experienced by a particle with charge of 
in the presence of an electric field 
Calculate the force experienced by a particle with charge of
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The force 
on a given charge 
in the presence of an electric field 
is given below as:
It is important to note that the force will be directed along the same direction as the electric field. Therefore, for our problem, we are able to write
The force
It is important to note that the force will be directed along the same direction as the electric field. Therefore, for our problem, we are able to write
Determine the force on a point charge of 
in an electric field of 
Determine the force on a point charge of
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Use the following form of the electric force equation:
Plug in values:
Use the following form of the electric force equation:
Plug in values:
An object deep in space of mass 
and charge 
accelerates at 
. Determine the electric field at this location.
An object deep in space of mass
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Use the following equation for electric force:
Plug in values:
Use the following equation for electric force:
Plug in values:
A 
charge of mass 
accelerates with 
. Determine the electric field.
A
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Using 
and 
Combining equations:
Solving for 
Converting 
to 
, 
to 
and plugging in values
Using
Combining equations:
Solving for
Converting
An observer is 
away from a negatively charged sphere. How will the electric field change as they move closer to the sphere?
An observer is
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As one moves closer to a negative charge, the electric field increases in the direction of the negative charge.
As one moves closer to a negative charge, the electric field increases in the direction of the negative charge.
An electron is moved in a perfect circle, with a negative point charge in the center. Determine the work done by the negative point charge.
An electron is moved in a perfect circle, with a negative point charge in the center. Determine the work done by the negative point charge.
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There will be no work done. The point charge at the center is emitting an electric field towards itself. If the electron is moved in a circle around it, it will have moved perpendicular to the force the entire time, and thus no work has been done.
There will be no work done. The point charge at the center is emitting an electric field towards itself. If the electron is moved in a circle around it, it will have moved perpendicular to the force the entire time, and thus no work has been done.
Suppose I have a uniform electric field within a parallel plate capacitor with field strength of 
.
Suppose the capacitor's plates are 
in length and the space between the plates is 
.
Determine the magnitude of force experienced by an individual electron placed in this field and the direction. Assume the charge of an electron is 
Suppose I have a uniform electric field within a parallel plate capacitor with field strength of
Suppose the capacitor's plates are
Determine the magnitude of force experienced by an individual electron placed in this field and the direction. Assume the charge of an electron is
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Recall that the formula for the magnitude of force 
is given by:
Where 
is the electric field strength and 
is the charge.
Since the electric field strength is constant,
To determine direction, remember that electrons will move towards the positively charged plates since electrons are negatively charged.
Recall that the formula for the magnitude of force
Where
Since the electric field strength is constant,
To determine direction, remember that electrons will move towards the positively charged plates since electrons are negatively charged.