Name: 
 

Ch 23 Series and parallel Circuits



True/False (Value 8)
Indicate whether the statement is true or false.
 

 1. 

Voltage dividers are often used with sensors, such as photosensors.
 

 2. 

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

 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. 

Arc fault circuit interrupters use electronic detectors to respond to the electric signals associated with arcing; they can shut down a circuit in many cases where a circuit breaker would react.
 

 8. 

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

Multiple Choice (Value 14)
Identify the choice that best completes the statement or answers the question.
 

 9. 

A 10.0-W resistor, 20.0-W resistor, and 25.0-W resistor are connected in series across a 110-V supply. Calculate the current in the circuit.
a.
2.0 A
c.
55 A
b.
4.5 A
d.
11 A
 

 10. 

mc010-1.jpg
A 10-W resistor and a 30-W resistor are connected in series across a 100-V battery. In another combination, a 10-W resistor and a 30-W resistor are connected in parallel across a 100-V battery. The ratio of the voltage drop across the 10-W resistor in the series combination to that of the 10-W resistance connected in parallel is:
a.
mc010-2.jpg
c.
mc010-4.jpg
b.
mc010-3.jpg
d.
mc010-5.jpg
 

 11. 

A 2.00-W resistor and a 12.0-W resistor are connected in parallel across a 20.0-V battery. What is the current flowing through the 2.00-W resistor?
a.
1.67 A
c.
11.6 A
b.
1.40 A
d.
10.0 A
 

 12. 

A short piece of metal that melts when a large current passes through it is a:
a.
circuit breaker
c.
relay
b.
surge suppressor
d.
fuse
 

 13. 

An automatic switch that opens when the current reaches a set value is called:
a.
surge suppressor
c.
circuit breaker
b.
relay
d.
fuse
 

 14. 

Which device measures the current in a circuit?
a.
Ammeter
c.
Amplifier
b.
Voltmeter
d.
Rheostat
 

 15. 

A 4.0-W resistor, an 8.0-W resistor, and a 10.0-W resistor are connected in series across an 11-V battery. What value of resistance must be connected in series with the circuit to decrease the current in the circuit by 50.0%?
a.
11 W
c.
33 W
b.
22 W
d.
44 W
 

 16. 

A circuit consists of two resistors, Ra and Rb, connected in series with a 20-V battery. What should be the ratio of mc016-1.jpg so that the voltage drop across Rb is 18 V?
a.
mc016-4.jpg
c.
mc016-6.jpg
b.
mc016-5.jpg
d.
mc016-7.jpg
 

 17. 

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

 18. 

A/An _____ is described as a low resistance device connected in series that is used to measure current.
a.
ammeter
c.
fuse
b.
circuit breaker
d.
voltmeter
 

 19. 

_____ 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
 

 20. 

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
 

 21. 

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
 

 22. 

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 (Value 5)
 
 
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
 

 23. 

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

 24. 

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

 25. 

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

 26. 

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

 27. 

a type of circuit in which there are several current paths
 

Problem
 

 28. 

pr028-1.jpg

Two resistors of 10 W and 11 W are connected in parallel. A 30-W resistor is connected in series with the parallel arrangement. This combination is connected across a 130-V battery. The internal resistance of the battery is 0.9 W. Find the current through the 11-W resistor.
 

 29. 

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.
 

 30. 

A 10 ohm, a 15 ohm, and a 5 ohm resistor are connected in a series circuit with a 90 V battery.  What is the equivalent resistance of the circuit?  What is the current in the circuit?
 

 31. 

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.
 

 32. 

A student makes a voltage divider from a 45 V battery, a 475 ohm resistor, and a 235 ohm resistor.  The output is measured across the smaller resistor.  What is the voltage?
 



 
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