Engineering Fundamentals: An Introduction to Engineering, 4th ed.c

348 Chapter 12 Electric Current and Related Parameters

To increase the voltage output, batteries are often placed in a series arrangement. If we

connect batteries in a series arrangement, the batteries will produce a net voltage, which will be

the sum of the individual batteries placed in series. For example, if we were to connect four

1.5-volt batteries in series, the resulting potential will be 6 volts, as shown in Figure 12.1. Bat-

teries connected in a parallel arrangement, as shown in Figure 12.2, produce the same voltage,

but more current.

Photoemission

Photoemisssion is another principle used to generate electricity. When light strikes a sur-

face that has certain properties, electrons can be freed; thus electric power is generated.

You may have seen examples of photovoltaic devices such as light meters used in photog-

raphy, photovoltaic cells in hand-held calculators, and solar cells used in remote areas to

generate electricity.

Photovoltaic devices are becoming increasingly common in many applications because

they do not pollute the environment. In general, there are two ways in which the sun’s radia-

tion is converted to electricity: photothermal and photovoltaic. In photothermal plants, solar

radiation (the sun’s radiation) is used to make steam by heating water flowing through a pipe.

The pipe runs through a parabolic solar collector, and then the steam is used to drive a gener-

ator. In a photovoltaic cell, the light is converted directly to electricity. Photovoltaic cells, which

are made of gallium arsenide, have conversion efficiencies of approximately 20%. The cells are

1.5 volts 1.5 volts 1.5 volts

6 volts

1.5 volts 



6 volts





   

■Figure 12.1

Batteries connected in a series

arrangement.

1.5

volts

1.5

volts

1.5

volts

1.5 volts

1.5

volts





1.5 volts





















■Figure 12.2

Batteries connected in a parallel

arrangement.

Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s).

圀圀圀⸀夀䄀娀䐀䄀一倀刀䔀匀匀⸀䌀伀䴀圀圀圀⸀夀䄀娀䐀䄀一倀刀䔀匀匀⸀䌀伀䴀