Practice Problems with Parallel Circuits
1. As more and more resistors are added in parallel to a circuit, the
equivalent resistance of the circuit ____________ (increases,
decreases) and the total current of the circuit ____________
(increases, decreases).
2. Three identical light bulbs are connected to a battery as shown
below. P, Q, X, Y and Z represent locations along the circuit.
Which one of the following statements is true?
a. The current at Y is greater than the current at
Q.
b. The current at Y is greater than the current at
P.
c. The current at Y is greater than the current at Z.
d. The current at P is greater than the current at Q.
e. The current at Q is greater than the current at P.
f. The current is the same at all locations.
3. Three identical light bulbs are connected to a battery as shown
below. P, Q, X, Y and Z represent locations along the circuit. At
which location(s), if any, will the current be ...
a. ... the same as at X?
b. ... the same as at Q?
c. ... the same as at Y?
d. ... less than at Q?
e. ... less than at P?
f. ... twice that at Z?
g. ... three times that at Y?
4. Which adjustments could be made to the circuit below that
would decrease the current in the
battery?
List all that apply.
a. Increase the resistance of bulb X.
b. Decrease the resistance of bulb X.
c. Increase the resistance of bulb Z.
d. Decrease the resistance of bulb Z.
e. Increase the voltage of the battery.
f. Decrease the voltage of the battery.
g. Remove bulb Y.
5. A 12-V battery , a 12-ohm resistor and a 4-ohm resistor are
connected as shown. The current in the 12-ohm resistor is ____
that in the 4-ohm resistor.
a. 1/3 b. 1/2 c. 2/3
d. the same as e. 1.5 times
f. twice
g. three times
h. four times
6. A 12-V battery , a 12-ohm resistor and a 4-ohm resistor are
connected as shown. The voltage drop across the 12-ohm resistor
is ____ that across the 4-ohm resistor.
a. 1/3 b. 1/2 c. 2/3
d. the same as e. 1.5 times
f. twice
g. three times
h. four times
7. A 12-V battery and a 12-ohm resistor are connected as shown in
circuit. A 6-ohm resistor is added to the 12-ohm resistor to create
circuit Y as shown. The voltage drop across the 6-ohm resistor in
circuit Y is ____ that across the resistor in X.
a. larger than
b. smaller than
c. the same as
8. Use your understanding of equivalent resistance to complete the
following statements:
a. Two 6- resistors placed in parallel would provide a resistance
which is equivalent to one _____- resistor.
b. Three 6- resistors placed in parallel would provide a resistance
which is equivalent to one _____- resistor.
c. Three 8- resistors placed in parallel would provide a resistance
which is equivalent to one _____- resistor.
d. Three resistors with resistance values of 2- , 4- , and 6- are
placed in parallel. These would provide a resistance which is
equivalent to one _____- resistor.
e. Three resistors with resistance values of 5- , 6- , and 7- are
placed in parallel. These would provide a resistance which is
equivalent to one _____- resistor.
f. Three resistors with resistance values of 12- , 6- , and 21- are
placed in parallel. These would provide a resistance which is
equivalent to one _____- resistor.
9. Based on your answers to the above question, complete the
following statement:
The overall or equivalent resistance of three resistors placed in
parallel will be _____.
a. greater than the resistance of the biggest R value of the three.
b. less than the resistance of the smallest R value of the three.
c. somewhere in between the smallest R and the biggest R value of
the three.
d. ... nonsense! No such generalization can be made. The results
vary.
10. Three resistors are connected in parallel. If placed in a circuit
with a 12-volt power supply. Determine the equivalent resistance,
the total circuit current, and the voltage drop across and current in
each resistor.