PHY_10_34_V2_DM_Charges in E

Problem Solving:

An electron is placed in an uniform electric field of 4.5x10^5N/C created by two parallel plates that are 5 cm apart. The electron accelerates from rest at the negative plate.

     (i)            Draw a diagram of this problem

   (ii)            What is the net force and acceleration acting on the  electron?

 (iii)             Calculate the final speed and the kinetic energy of the electron after travelling a distance of 5 cm

Reading task: Watch the video (0-1,25 min) AND ANSWER THE QUESTIONS:

https://www.youtube.com/watch?v=U1amW7S1fcI

1. What is CRT?
2. For what reason an electron gun is used?
3. Responsibility of the vertical and horizontal  plates…
4. How do we call the screen on which  electrons gives a bright spot

Multiple Choice questions Charges in Electric field:

Data needed to answer questions can be found in the Data, formulae and relationships sheet.

1    Which statement defines electric field strength between two parallel plates?                              [1]

A   Electric field strength is equal to the charge per unit distance between the plates.

B   Electric field strength is equal to the force per unit charge.

C   Electric field strength is equal to force times the distance between the plates.

D   Electric field strength is equal to the potential difference times the distance
between the plates.

2    Which diagram correctly shows the electric field between two charged plates?

                                                                                                                                                  [1]

3    The diagram shows two parallel, charged plates.

Which statement about the electric field at points P, Q and R is correct?                                   [1]

A   The field at P is greater than the field at Q and R.

B   The field at P is less than the field at Q and R.

C   The fields at P and Q are equal but greater than the field at R.

D   The fields at all points P, Q and R are all equal.

4    There is a potential difference of 200 V across a pair of parallel plates which are 4.00 cm apart.
Calculate the force on a charge of 2.50 nC which is between the plates.

A   2.00 ´ 10⁻⁹ N

B   1.25 ´ 10⁻⁷ N

C   2.00 ´ 10⁻⁷ N

D   1.25 ´ 10⁻⁵ N                                                                                                                    [1]

5    Which diagram correctly shows the electric field between two parallel plates
and the path of an electron as it passes between the plates?

       [1]

Structured problem Solving: Charges in Electric field

 6  State two possible SI units for electric field strength.                                                               [2]

 7  A +5.0 ´ 10⁻⁸ C point charge experiences a force of 1.5 ´ 10⁻³ N when placed in a uniform
electric field. Calculate the electric field strength.                                                                        

[2]

 8  Calculate the force experienced by an oil droplet with a charge of 3.2 ´ 10⁻¹⁹ C due to a
uniform electric field of strength 5.0 ´ 10⁵ V m⁻¹.                                                                       

[2]

   9 The diagram shows two parallel, horizontal plates separated by a vertical distance of 3.0 cm.
The potential difference between the plates is 600 V.

a    Calculate the magnitude and direction of the electric field between the plates.                      [3]

b    Describe the electric field between the plates.                                                                    [2]

c    An oil droplet of weight 6.4 ´ 10⁻¹⁵ N is held stationary between the two plates.

i     State whether the charge on the droplet is positive or negative.
Explain your answer.                                                                                                  [2]

ii    Determine the charge on the oil droplet.                                                                       [2]

10  A proton is travelling at right angles to an electric field of strength 2.40 ´ 10^–6 V m^–1.

a    Calculate the force on the proton due to the electric field.                                                   [2]

b    Calculate the acceleration of the proton in the direction of the field.                                    [2]

c    Write down the acceleration of the proton at right angles to the field.                                  [1]

11  A pair of parallel plates are 5.0 cm apart and are connected to a 200 V supply. A particle of
dust between the plates experiences a force, due to the field, of 3.2 ´ 10⁻⁴ N.

Calculate the charge on the dust particle.                                                                                 [3]

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