# Physics

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1. A charge moves a distance of 1.7 cm in the
direction of a uniform electric field having
a magnitude of 200 N/C. The electrical
potential energy of the charge decreases by
9.69095 × 10−19 J as it moves.
Find the magnitude of the charge on the
moving particle. (Hint: The electrical poten-
tial energy depends on the distance moved in
the direction of the field.)

2. Initially, both metal spheres are neutral.
In a charging process, 1 × 1013 electrons are
removed from one metal sphere and placed on
a second sphere. Then the electrical poten-
tial energy associated with the two spheres is
found to be −0.061 J .
The Coulomb constant is 8.98755 ×
109 N · m2/C2 and the charge on an electron
is 1.6 × 10−19 C.
What is the distance between the two
spheres?

3. It takes 119 J of work to move 2.4 C of charge
from a positive plate to a negative plate.
What voltage difference exists between the
plates?

4The magnitude of a uniform electric field be-
tween the two plates is about 2 × 105 N/C.
If the distance between these plates is
0.1 cm, find the potential difference between
the plates.

5A force of 3.60 × 10−2 N is needed to move a
charge of 56.0 μC a distance of 25.0 cm in the
direction of a uniform electric field.
What is the potential difference that will
provide this force?

6An electron moves from one plate of a capaci-
tor to another, through a potential difference
of 2495 V.
a) Find the speed with which the electron
strikes the positive plate.

7b) If a proton moves from the positive plate to
the negative plate, find the speed with which
the proton strikes the negative plate.

008
A proton is accelerated from rest through a
potential difference of 119 V.
Calculate the final speed of this proton.

9. The three charges shown in the figure are
located at the vertices of an isosceles triangle.
The Coulomb constant is 8.98755 ×
109 N · m2/C2 and the acceleration of grav-
ity is 9.8 m/s2 .
4.1 cm
4.1 cm
1.4 cm
+
− − 3.3 × 10−9 C 3.3 × 10−9 C
5.1 × 10−9 C
Calculate the electric potential at the mid-
point of the base if the magnitude of the posi-
tive charge is 5.1×10−9 C and the magnitude
of the negative charges are 3.3 × 10−9 C.

10. An electron that is initially 54 cm away from
a proton is displaced to another point.
The Coulomb constant is 8.98755 ×
109 Nm2/C2 and the acceleration of gravity
is 9.8 m/s2.
If the change in the electrical potential
energy as a result of this movement is
2.7 × 10−28 J, what is the final distance be-
tween the electron and the proton?

11A potential difference of 117.0 V exists across
the plates of a capacitor when the charge on
each plate is 429.0 μC.
What is the capacitance?

12A parallel-plate capacitor has a plate area of
188 cm2 and a plate separation of 0.0420 mm.
The permittivity of a vacuum is 8.85419 ×
10−12 C2/N · m2.
a) Determine the capacitance.

13b) Determine the potential difference when
the charge on the capacitor is 530.0 pC.

14A parallel-plate capacitor has a capacitance
of 0.28 μF and is to be operated at 6500 V.
a) Calculate the charge stored.

15b) What is the electrical potential energy
stored in the capacitor at the operating po-
tential difference?

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It is 2013 and this is easy for 8 th graders