Name: 
 

Ch 23: Series and Parallel Circuits



True/False
Indicate whether the statement is true or false.
 

 1. 

A fuse is an automatic switch that opens when the current reaches a threshold value.
 

 2. 

To measure the potential drop across a resistor, a voltmeter is connected in parallel with a resistor.
 

 3. 

Without a fuse or circuit breaker, the current caused by a short circuit easily could start a fire.
 

 4. 

A ground-fault interrupter in an electric outlet prevents injuries because it contains an electronic circuit that detects differences in current caused by an extra path and opens the circuit.
 

 5. 

It is necessary to understand series and parallel circuits to fully understand residential wiring.
 

 6. 

All household devices are connected in parallel because they are designed to operate at the same voltage.
 

 7. 

A circuit breaker is a short piece of metal that melts when a current that is too large passes through it.
 

 8. 

Fuses and circuit breakers protect against the large currents created by a short circuit.
 

 9. 

Ammeters have a very high resistance so as to cause the smallest possible change in currents and voltages in the circuit.
 

Multiple Choice
Identify the choice that best completes the statement or answers the question.
 

 10. 

If a resistor is added to a series circuit, the equivalent resistance:
a.
increases
c.
remains the same
b.
decreases
d.
becomes zero
 

 11. 

If a resistor is added to a parallel circuit, the equivalent resistance:
a.
increases
c.
remains the same
b.
decreases
d.
becomes zero
 

 12. 

Ideally, the resistance of an ammeter should be:
a.
high
c.
more than 20 W
b.
medium
d.
zero
 

 13. 

A/An _____ is described as an automatic switch that acts as a safeguard in an electric current.
a.
circuit breaker
c.
ground fault interrupter
b.
fuse
d.
voltage divider
 

 14. 

A parallel circuit has four branch currents: 120 mA, 380 mA, 250 mA, and 2.1 A.  How much current is supplied by the source?
a.
.029 A
c.
2.9 A
b.
0.29 A
d.
29 A
 

 15. 

A/An _____ is described as a piece of metal that acts as a safety device in a circuit which melts and stops the flow of current.
a.
circuit breaker
c.
ground fault interrupter
b.
fuse
d.
short circuit
 

 16. 

_____ is described as the sum of all the individual resistances in a series.
a.
Equivalent resistance
c.
Series circuit
b.
Parallel circuit
d.
Short circuit
 

 17. 

A/An _____ is described as a device that detects current differences and then opens the circuit preventing electrocution.
a.
circuit breaker
c.
ground fault interrupter
b.
fuse
d.
short circuit
 

 18. 

A/An _____ is a device that is used to measure the current in any branch or part of a circuit.
a.
ammeter
c.
resistor
b.
volt meter
d.
battery
 

 19. 

A/An _____ occurs when a very low resistance circuit is formed and can easily start a fire.
a.
parallel circuit
c.
short circuit
b.
series circuit
d.
voltage divider
 

 20. 

A series circuit has four resistors.  The current through one resistor is 810 mA.  How much current is supplied by the source?
a.
.810 mA
c.
81.0 mA
b.
8.10 mA
d.
810 mA
 

 21. 

There are 11 lights in series, and they are in series with 2 lights in parallel.  If the 13 lights are identical, which of them will burn brightest?
a.
11 lights
c.
all 13 lights
b.
2 lights
d.
none will be brightest
 

Matching
 
 
Define the following terms by matching them to the correct definition.
a.
ammeter
f.
parallel circuit
b.
circuit breaker
g.
series circuit
c.
equivalent resistance
h.
short circuit
d.
fuse
i.
voltage divider
e.
ground fault interrupter
j.
voltmeter
 

 22. 

device used to measure voltage drop across any part of a circuit
 

 23. 

an automatic switch that acts as a safeguard in an electric current
 

 24. 

a low resistance device connected in series that is used to measure current
 

 25. 

device that detects current differences; opens circuit preventing electrocution
 

 26. 

a piece of metal that acts as a safety device in a circuit; melts and stops flow
 

Short Answer
 

 27. 

Compare and contrast the voltages and the currents in series and parallel circuits.
 

 28. 

A 12 ohm, 2-W resistor is connected in parallel with a 6.0 ohm, 4-W resistor.  Which will become hotter if the voltage across them keeps increasing?
 

 29. 

Compare the voltage drop in a voltage divider to a volume control in a CD player.
 

Problem
 

 30. 

Three 20 ohm resistors are connected in series across a 120 V generator. What is the equivalent resistance of the circuit?  What is the current of the circuit?
 

 31. 

Three resistors, 60.0 ohms, 30.0 ohms, and 20.0 ohms, are connected in parallel across a
90.0 V battery. 
a) Find the current through each branch of the circuit.
b) Find the equivalent resistance of the circuit.
c) Find the current through the battery.
 

 32. 

Three 15.0 ohm resistors are connected in parallel across a 30.0 V battery. 
a) Find the current through each branch of the circuit.
b) Find the equivalent resistance of the circuit.
c) Find the current through the battery.
 

 33. 

A string of holiday lights has ten bulbs with equal resistances connected in a series.  When the string of lights is connected to a 120 V outlet, the current through the bulbs is 0.06 A.  What is the equivalent resistance of the circuit?  What is the resistance of each bulb?
 

 34. 

Three resistors, 120.0 ohms, 60.0 ohms, and 40.0 ohms are connected in a parallel across a 120.0 V battery. 
a) Find the equivalent resistance of the circuit.
b) Find the current through the entire circuit.
c) Find the current through each branch of the entire circuit.
 

 35. 

Four resistors, 50.0 ohms, 40.0 ohms, 30.0 ohms, and 20.0 ohms, are connected in a parallel across a 120.0 V battery. 
a) Find the current through each branch of the circuit.
b) Find the equivalent resistance of the circuit.
c) Find the current through the battery.
 



 
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