Charge between parallel plates

In summary: Hence,y=0.01=0.5at^2 => t^2=0.02/a => t=sqrt(0.02/a)In summary, the electric field between the plates can be calculated using the formula E=V/d, which in this case equals 2x10^5 V/m. The force on a charge of -1.602x10^-19C in this field can be found using the formula F=qE, which results in a value of 0.3204 N. The acceleration of this charge is then calculated using the formula a=F/Me, resulting in a value of 3.517x10^29 m/s. The time it takes for the charge to
  • #1
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Homework Statement
Given a charge -e moving through a set of charged plates at a velocity of 0.8 x10^7 m/s. The plates have a voltage of 4000v, how long can the plates be without the charge -e impacting one of them?
-e = -1.602 x 10^-6 C
Me = 9.11 x 10^-31 kg
Relevant Equations
E=v/d
F=qE=ma
Electric field between the plates
V=4x10^3
d=0.02
E=4x10^3/0.02
E=2x10^5 V/m

Calculate the force on charge -e
-e = -1.602x10^-6
Me = 9.11x10^-31
F=qE
F=(1.602x10^-6)(2x10^5)
F=0.3204 N

Using F=ma
a=F/Me
a=0.3204/9.11x10^-31
a=3.517x10^29 m/s

Time = distance / speed
T=.01 (half distance of plates with charge in the middle) / 3.517x10^29
T =2.84x10^-32 seconds

Calculate the distance the charge would move at 0.8x10^7 m/s in 2.84x10^-32 seconds

Distance = speed x time
Distance = 0.8x10^7 x 2.84x10^-32
Distance = 2.272x10-25 mtrs
I think I have royally screwed up my calculations somewhere here as a) the charge is moving substantially faster than the speed of light. And b) the length or distance seems really really small?
 
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  • #2
A few points to consider...

If 'e' is meant to be the elementary charge, then e = 1.602x10⁻¹⁹C, not 1.602x10⁻⁶C.

The particle (it may not be an electron) behaves like a simple projectile, with an initial horizonal velocity, in a gravitational field. Make sure you know how to do simple projectile calculations!

Watch out for careless mistakes. E.g the unit for acceleration is not m/s!
 
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  • #3
Except the mistake regarding the value of acceleration due to the electric field, which mistake is due to wrong charge of electron as spotted by @Steve4Physics , you have done another mistake in calculating the time to move vertically from the middle up (or down) to the plate due to the electric field.

You should use the formula $$y=\frac{1}{2}at^2$$ and not $$y=at$$ which is the one you used (y=0.01 since that charge starts from middle).
 
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1. What is the formula for calculating the electric field between parallel plates?

The formula for calculating the electric field between parallel plates is E = V/d, where E is the electric field, V is the potential difference between the plates, and d is the distance between the plates.

2. How does the distance between parallel plates affect the electric field?

The electric field between parallel plates is directly proportional to the distance between the plates. This means that as the distance increases, the electric field decreases, and vice versa.

3. What is the relationship between charge and electric field between parallel plates?

The electric field between parallel plates is directly proportional to the charge on the plates. This means that as the charge increases, the electric field also increases.

4. What is the significance of the direction of the electric field between parallel plates?

The direction of the electric field between parallel plates is always perpendicular to the plates. This means that the electric field lines are straight and do not curve towards or away from the plates.

5. How does the presence of dielectric material between parallel plates affect the electric field?

The presence of dielectric material between parallel plates increases the capacitance and decreases the electric field between the plates. This is because the dielectric material reduces the electric field by polarizing and storing electric charge.

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