Relationship between E and V Flashcards
Consider a uniform electric field between a pair of parallel metal plates. The electric field strength is E. Consider a charge +Q being moved from point A to point B in the uniform electric field by a force F. What is the work done by that force?
W = Fd
let d be some small change in a distance, delta x so the force remains constant from point A to B
delta W=F(delta x)
if E=F/Q then F = -EQ
(minus because work has to be done against the electric field)
substitute into equation 1
delta W = -EQ(delta x)
Since the electric potential at B is higher than A, let the potential difference between A and B be delta V
if V = W/Q then delta W = (delta V)Q
therefore there are two ways to find the work done.
delta W = (delta V)Q
delta W = -EQ(delta x)
Consider a uniform electric field between a pair of parallel metal plates. The electric field strength is E. Consider a charge +Q being moved from point A to point B in the uniform electric field by a force F. Using 2 equation for work derive an equation for potential gradient. Therefor what other unit can be used to describe electric field strength.
- EQ(delta x) = Q(delta V)
- EQ(delta x)/Q = Q(delta V)/Q
- E(delta x) = delta V
E = - delta V/ (delta x)
Hence electric field strength can be written in volts per meter (V m^-1).
How is potential gradient in a electric field related to field strength.
The electric field strength at a point in an electric field is therefore numerically equal to the potential gradient at that point.
Consider the electric field produced between two parallel plates. The separation between the plates is d and the potential difference across the plates is V. What equation can be used to determine the electric field strength between the two parallel plate conductors?
E = -V/d
Suppose an electron is projected horizontally between a pair of parallel metal plates with a velocity, v. What is the direction of the force experienced by the electron as it enters the electric field.
The electron experiences a force towards the positive plate. If the positive plate is at the bottom, it will experience a downwards force.
Suppose an electron is projected horizontally between a pair of parallel metal plates with a velocity, v. And the electrons experiences a force of F acting downwards towards the positive plate as it enters the electric field. What is the vertical component of the velocity just before it enters the field?
The vertical component of the electrons velocity is zero just before it enters the field because it was projected horizontally.
Suppose an electron is projected horizontally between a pair of parallel metal plates with a velocity, v. And the electrons experiences a force of F acting downwards towards the positive plate as it enters the electric field. What direction does the electron accelerate when it enters the field?
Upon entering the field the downwards force acting on the electron causes it to accelerate toward the positive plate.
Suppose an electron is projected horizontally between a pair of parallel metal plates with a velocity, v. And the electrons experiences a force of F acting downwards towards the positive plate as it enters the electric field. What is the horizontal component of the velocity of the electron as it enters the field?
The horizontal component of the electrons in the electron field is the same as the velocity at which it was projected, v. Because the force is not acting in a horizontal direction the horizontal component of the velocity is unaffected there v is unchanged.
Suppose an electron is projected horizontally between a pair of parallel metal plates with a velocity, v. And the electrons experiences a force of F acting downwards towards the positive plate as it enters the electric field. What kind of path would the electron follow?
The electron follows a curved (parabolic) path as it passes through the electric field.
Suppose an electron is projected horizontally between a pair of parallel metal plates with a velocity, v. And the electrons experiences a force of F acting downwards towards the positive plate as it enters the electric field. What is the path of the electron after it leaves the electric field?
Once the electron is outside the electric field it continues moving in a straight line with the velocity it possessed coming out of the field.
Suppose a mass m is projected horizontally with a velocity vh. What is the initial vertical component of its velocity?
The initial vertical component, vv of its velocity is zero.
Suppose a mass m is projected horizontally with a velocity vh. What direction is the force it experiences? What does that say about it’s acceleration?
It experiences the force of gravity (mg) pulling it downwards toward the earth (acting vertically).
The mass will accelerate vertically.
Suppose a mass m is projected horizontally with a velocity vh. What is the effect on the vertical component of the velocity as it falls through the air?
The vertical component of the velocity increases from 0.
Suppose a mass m is projected horizontally with a velocity vh. Assuming air resistance as zero describe the changes in the horizontal component of the velocity. Hence what type of path will the mass take?
The horizontally component of the velocity vh is the intial velocity it was projected horizontally at. And it remains constant since there is no force acting horizontally as gravity acts vertically.
The resultant of the constant horizontal component and the increasing vertical component of velocity enables the mass to travel a parabolic (or curved) path.
