Download Electric Potential 1. A negative charge q is fired through small hole

1. A negative charge q is fired through small hole in the negative plate as shown in the
sketch. The oppositely charged metallic plates have charge Q and area A each. (a) Draw
and label the direction of electric force and field on the charge q when it is moving in
between the oppositely charged plates. (b) Is the charge speeding up, slowing down or
neither as it moves toward the positively charged plate? Use the concept of force on the
charge to explain it.
-
q
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Electric Potential
(c) Write down an equation of potential energy of the charge when it is at some distance d from the negative plate. Is the
potential energy positive or negative? Now explain why the charge is either speeding up, slowing down or neither using the
concept of potential energy.
(d) how is the change in potential energy is related to the change in KE of the charge?
(e) Is the electric field in between the plates same or different? Explain by writing an equation.
(f) Is the electric potential (not potential energy) of the charge changing when it moves towards the positive plate?
Is it increasing or decreasing? Explain with an equation.
2. The sketch shows a potential vs position graph. By using the fact that value of electric field, Ex 
graph on the right. Add appropriate scale on vertical axis.
20
V(V)
V
, sketch Ex vs x
x
Ex(N/m)
10
0
1
x(m)
2
0
1
x(m)
2
3. The sketch shows a map of equipotential lines at different positions. It is also known as contour map. Estimate the
magnitude of electric field at points a and b. Also, sketch the direction of the electric fields at these point.
10V
0V
20V
30V
a
0
1
40V
50V
5
6
b
2
3
4
x(m)
4. A capacitor is charged until the electric field strength inside the capacitor is 5000 V/m then disconnected from battery. A
dielectric is inserted between the plates of the capacitor and the field is re-measured. The new reading shows the strength
is 1000 V/m.
a) Visualize the charges inside the capacitor
before inserting the dielectric and after inserting it.
b) By what factor does the charge increase or decrease
after the dielectric is inserted? Or does it stay same?
c) By what factor does the potential difference increase or decrease
after the dielectric is inserted? Or does it stay same?