Download Electrostatics worksheet

Electrostatics Worksheet
1. The diagram below is of a hydrogen atom.
a) Label the proton in the nucleus with a
positive sign and the orbital electron with
a negative sign.
b) The electrical interaction between the
nucleus and the electron is a force of
(attraction, repulsion).
2. The outer electrons in metals are not tightly
bound to the atomic nuclei. They are free to roam
in the material. Such materials are good _____.
3. How many electrons are in 1.92 x 10–18 C?
4. By convention, what is the charge of
a) Electrons
b) Protons c) Neutrons?
5. Like charges ____ and opposite charges ____.
6. What is the principle of conservation of
charge?
7. The ________ of many atoms are bound very
loosely to an atom and can be easily dislodged.
a) Outermost electrons
b) Innermost electrons
c) Outermost protons
d) Innermost protons
8. A charged atom is called a (n) ________.
9. Define semiconductor.
c) Combing your hair with a plastic comb
d) Touching your hand to a slightly charged
metal plate
12. By how much does the electric force between
a pair of charged bodies change when their
separation is
a) doubled? b) tripled? c) cut in half?
d) By how much does the electric force
between a pair of charged bodies change
when each charge is tripled?
13. The most common isotope of hydrogen
contains a proton and an electron separated by
about 5.0 x 10–11 m. The mass of a proton is
approximately 1.67 x 10–27 kg. The mass of the
electron is approximately 9.11 x 10–31 kg.
a) Use Newton's law of universal gravitation
(F = Gm1m2/d2; G = 6.67 x 10–11) to
calculate the gravitational force between
the electron and proton in the hydrogen
atom.
b) Use 1.6 x 10–19 C as the elementary unit of
charge to determine the force of attraction
between the two particles.
c) How many orders of magnitude greater is
the electric force between the two
particles than the gravitational force
between the two particles? How important
are gravitational force effects in this case?
14. Two charged spheres are on a frictionless
horizontal surface. One has a charge of +3.0 μC,
the other a +6.0 μC charge. Sketch the two
spheres, showing all forces on them. Make the
length of your force arrows proportional to the
strength of the forces.
10. Classify the following as a conductor, an
insulator, or a semiconductor.
a) Aluminum
b) Glass
c) Copper
d) Rubber
e) Germanium
f) Silicon
15. Two positive charges of 6.0 x 10–6 C are
separated by 0.50 m. Draw a force diagram for
each of the charges, considering only electrostatic
forces. What is the magnitude of the force
between the charges? Is this force repulsive or
attractive?
11. Classify each of the following by writing F if
it is an example of charging an object by friction
and C if it is an example of charging an object by
contact.
a) Sliding across the seat of an automobile
b) Touching a charged rod to a metal sphere
16. A negative charge of 2.0 x 10–4 C and a
positive charge of 8.0 x 10–4 C are separated by
0.30 m. What is the magnitude of the force
between the charges? Is this force repulsive or
attractive?
Figure 1
Figure 2
q3
q1
q2
0.20 m
q3
0.15 m
17. Figure 1 shows three point charges that lie
along the x-axis. Determine the magnitude and
direction of the net electrostatic force on charge
q1. (q1 = +6.0 µC; q2 = –4.0 µC; q3 = – 7.0 µC)
18. Determine the magnitude and direction of the
net electrostatic force on charge q2 in Figure 2.
As part of the solution, include a force diagram.
(q1 = +45.0 µC; q2 = –12.0 µC; q3 = +18.0 µC)
19. Calculate the size of the force that would be
experienced by a 3.0 C charge placed into a
uniform electric field of strength 1.0 x 105 N/C.
20. A – 5.0 mC charge travels due south under the
influence of a 10. N force when placed into a
uniform electric field. What force would a
10. mC charge experience if placed in the same
field and in which direction would it move?
21. What is the magnitude of a point charge that
would create an electric field of 1.00 N/C at
points 1.00 m away?
22. Consider a fixed point charge of +2.00 μC.
What is the magnitude and direction of the
electric field at a point P, a distance of 0.100 m
away?
23. An electric field has an electric field strength
6000. N/C at a distance of 1.5 m. What is the
strength of the field at a distance of 6.0 m?
24. An alpha (α) particle is stationary in an
electric field such that the gravitational force
acting on it is equal to the electrostatic force.
(qα = 3.2 x 10–19 C and mα = 6.64 x 10–27 kg)
a) What is the direction of the electric field at
this point? (Use E = F/q where F = mg)
b) What is strength of the electric field?
c) If the field is located 0.25 m away, what is
the magnitude of the charge?
25. Determine the potential at a point 0.50 m
from a 20. µC point charge.
3.00 m
q2
3.00 m
q1
26. An electric field is parallel to the x-axis. What
is the magnitude of the electric field if the
potential difference between x = 1.0 m and
x = 2.5 m is found to be +900 V?
27. A charged droplet of mass 5.88 x 10–10 kg is
hovering motionless between two parallel plates.
The parallel plates create have a potential
difference of 24000 V and are 2.00 mm apart.
What is the charge on the particle?
28. Two parallel plates 2.1 mm apart, are charged
so that the potential difference between the plates
is 36 V.
a) What is the electric field strength between
the plates?
b) A small particle charge of +180 nC is
placed midway between the plates. Find
the force on the particle due to the electric
field.
29. A potential difference of 1.00 x 104 V exists
between two parallel plates which are separated
by 10.0 cm. An electron (me = 9.11 x 10–31 kg) is
released from the negative plate at the same
instant a proton (mp = 1.67 x 10–27 kg) is released
from the positive plate.
a) What is the electric field strength between
the plates?
b) What is the acceleration of each particle?
Answers
3) 12
13a) 4.1 x 10–47 N
13b) 9.2 x 10–8 N
39
13c) 2.2 x 10
15) 1.3 N repulsive
16) 16000 N attractive 17) 11.6 N right
18) 0.582 N, 21.8º NE
19) 0.30 N
20) 20 N, south
21) 1.11 x 10–10 C
22) 1.80 x 106 N/C
23) 375 N/C
24a) up
24b) 2.0 x 10–7 N/C 24c) 1.4 x 10–18 C
5
25) 3.6 x 10 V
26) 600 N/C 27) 4.8 x 10–16 C
28a) 17,000 N/C
28b) 0.0031 N
29a) 1.00 x 105 N/C
29b) p+ = 9.58 x 1012 m/s2, e- = 1.76 x 1016 m/s2