Name
Date
Electric Circuits
Parallel Circuits
Instructions: Do every problem using LEPA on a separate sheet of paper.
1. Three identical resistors are connected in parallel with each other. If the resistance of
each resistor is R ohms, what is the equivalent resistance of the circuit?
2. A 4-ohm resistor and an 8-ohm resistor are connected in parallel across a 9-volt battery.
a. What is the potential difference across the 4-ohm resistor?
b. What is the potential difference across the 8-ohm resistor?
c. What is the equivalent resistance of the circuit? 2.67 Ω
d. What is the total current leaving the battery? 3.38 A
3. A 2-ohm resistor, 6-ohm resistor and 9-ohm resistor are connected in parallel across an
18 volt battery.
a. What is the current flowing through the 2-ohm resistor? 9 A
b. What is the current flowing through the 6-ohm resistor? 3 A
c. What is the current flowing through the 9-ohm resistor? 2 A
d. What is the total current in the circuit? 14 A
e. What is the equivalent resistance of the circuit? 1.29 Ω
4. Two identical resistors are connected to a battery. If they are connected in parallel and
have an equivalent resistance of 40-ohms, what is the resistance on each resistor?
5. A physics student is given three 6-ohm resistors with instructions to create the circuit that
would have the lowest possible resistance. The correct circuit would be a
a. series circuit with an equivalent resistance of 18 Ω
b. series circuit with an equivalent resistance of 2 Ω
c. parallel circuit with an equivalent resistance of 18 Ω
d. parallel circuit with an equivalent resistance of 2 Ω
6. Which of the following has the smallest equivalent resistance?
a.
b.
c.
d.
7. A 3 Ω resistor is connected in parallel to an unknown resistor. It is connected to a 1.5 V
battery. The total current from the battery is 1.5 A. What is the resistance of the other
resistor? 1.5 Ω
8. What is the power through a 7 Ω resistor that is connected in parallel to a 4 Ω resistor if
the current through the 4 Ω resistor is 2 A? 9.14 W
9. Draw the following circuit diagram of a parallel circuit and find the potential difference,
current, resistance and power for each resistor and the whole circuit:
 A cell with unknown voltage, VT
 Three resistors
o A 15 Ω resistor
o A 10 Ω resistor
o A resistor with unknown resistance, R
 Three ammeters
o One measuring a current of 1.2 A through the 10 Ω resistor
o One measuring a current of 2.4 A through the unknown resistor
o One measuring the current from the battery
 One voltmeters
o One measuring the potential difference across the 10 Ω resistor