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PHYSICS: Electricity Problem Set
Solve the following problems on a separate sheet of paper. Correct Answers are at the end of the problem
set.
A. The Fundamental Charge / Conservation of Charge
1.
(I) What is the charge on an electron?
2.
(I) If a particle gained 1.2 x 107 electrons, what is the charge on the particle?
3.
(I) If a particle losses 1.5 x 104 electrons, what is the charge on the particle?
4.
(I) If a particle has a charge of +45 C, has it gained or lost electrons? How many electrons has it gained or lost?
5.
(I) If sphere A has a charge of +5 C and sphere B has a charge of +2 C, what is the charge on each sphere after
A is touched to B and then removed?
6.
(I) Sphere A has 4.5 x 104 extra electrons. It is brought into contact with sphere B, which has 3.5 x 104 electrons
missing. After the contact what is the charge on each sphere?
7.
(I) A small pith ball carries a charge of –2.5 x 10-6 C. How many excess electrons does this charge represent?
1) -1.6 x 10-19 C
7) 1.6 x 1013
2) -1.9 x 10-12 C
3) +2.4 x 10
-15
C
4) lost 2.8 x 1014
5) +3.5 C
6) -8.0 x 10-16 C
B. Coulomb’s Law / Electrostatic Force / Electric Fields
1.
(I) A positive force calculated from Coulomb’s Law indicates _______________.
2.
(I) A negative force calculated from Coulomb’s Law indicates _______________.
3.
(II) Two identical positive charges are moved twice as far apart from each other. How will the new force of
repulsion compare to the original force?
4.
(II) Two charges are move three times closer to each other. How will the force o between them change?
5.
(I) Two positive charges of 6.0 x 10-6 C are 0.30 m apart. What force exists between the two charges?
6.
(II) A force of 90.0 N exists between a +15C charge and a -15C charge. How far apart are the charges?
7.
(II) A negative charge of 6.0 x 10-6 C exerts an attractive force of 64.8 N on a second charge 0.05 m away. What
is the second charge?
8. (III) Determine the magnitude and direction of the net force on the middle charge shown below.
9.
(I) A positive test charge of 8.0 x 10-5 C is placed in a electric field. It experiences a force of 4.0 x 10 -3 N. What
is the electric field intensity at this point?
10. (II) A positive test charge of 5.0 x 10-4 C is placed in an electric field. The test charge experiences a force of
-5.0 x10-4 N. What is the field intensity and type of charge creating the electric field?
1) repulsion
2) attraction
3) ¼ as much
6) 15 cm
7) +3.0 x 10-6 C
8) 158 N right
4) 9 times
more
9) 50 N/C
5) 3.6 N
10) 1 N/C;
negative
C. Capacitance
1.
(I) The potential difference between two parallel plates is 120 V. They have equal and opposite charge
of magnitude 95 pC. What is the capacitance of the plates?
2. (I) A 7500 pF capacitor holds 16.6 x 10-8 C of charge. What is the voltage across the capacitor?
3. (I) How much charge flows from a 12.0 V battery when it is connected to a 9.00 µF capacitor?
4. (II) A 0.20 F capacitor is desired. What area must plates have if they are to be separated by a 2.2 mm
air gap?
1) 0.79 pF
2) 22.0 V
3) 1.08 x 10-4 C
4) 5.0 x 107 m2
D. Ohm’s Law / Electric Current / Electric Power
1.
(I) A resistance of 30 Ω is placed across a 90 V battery. What current flows?
2. (I) A motor with an operating resistance of 30 Ω is connected to a voltage source. The current in
the motor is 4.0 A. What is the voltage of the source?
3. (I) A transistor radio uses 0.2 A of current when it is operated by a 3 V battery. What is the
resistance of the radio?
4. (I) A current of 0.5 A flows through a lamp when it is connected to a 120 V source.
a. What is the resistance of the lamp?
b. What is the wattage of the lamp?
1) 3 A
2) 120 V
3) 15 Ω
4) a. 240 Ω b. 60 W