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23.7 Transformers Transformers do what their name implies-they transform voltages from one value to another (The term voltage is used rather than emf, because transformers have internal resistance). For example, many cell phones, laptops, video games, and power tools and small appliances have a transformer built into their plug-in unit (like that in Figure 23.26) that changes 120 V or 240 V AC into whatever voltage the device uses. Transformers are also used at several points in the power distribution systems, such as illustrated in Figure 23.27. Power is sent long distances at high voltages, because less current is required for a given amount of power, and this means less line loss, as was discussed previously. But high voltages pose greater hazards, so that transformers are employed to produce lower voltage at the user's location. Figure 23.26 The plug-in trancformer has become increacingly familiar with the proliferation of electronic devices that operate on voltages other than common 120 V AC. Mast are in the 3 to 12 V range. (credit: Shop Xtreme) 400 kV 13 kV 12 kV 240 V Power plant Step-up transformer High-voltage transmission line Step-down transformer (substation) Step-down transformer Figure 23.27 Transformers change voltages at several points in a power distribution system. Electric power is usually generated at greater than 10 kV, and transmitted long distances at voltages over 200 kV-sometimes as great as 700 kV-to limit energy lasses. Local power distribution to neighborhoods or industries goes through a substation and is sent short distances at voltages ranging from 5 to 13 kV. This is reduced to 120, 240, or 480 V for safety at the individual user site.

23.7 Transformers Transformers do what their name implies-they transform voltages from one value to another (The term voltage is used rather than emf, because transformers have internal resistance). For example, many cell phones, laptops, video games, and power tools and small appliances have a transformer built into their plug-in unit (like that in Figure 23.26) that changes 120 V or 240 V AC into whatever voltage the device uses. Transformers are also used at several points in the power distribution systems, such as illustrated in Figure 23.27. Power is sent long distances at high voltages, because less current is required for a given amount of power, and this means less line loss, as was discussed previously. But high voltages pose greater hazards, so that transformers are employed to produce lower voltage at the user's location. Figure 23.26 The plug-in trancformer has become increacingly familiar with the proliferation of electronic devices that operate on voltages other than common 120 V AC. Mast are in the 3 to 12 V range. (credit: Shop Xtreme) 400 kV 13 kV 12 kV 240 V Power plant Step-up transformer High-voltage transmission line Step-down transformer (substation) Step-down transformer Figure 23.27 Transformers change voltages at several points in a power distribution system. Electric power is usually generated at greater than 10 kV, and transmitted long distances at voltages over 200 kV-sometimes as great as 700 kV-to limit energy lasses. Local power distribution to neighborhoods or industries goes through a substation and is sent short distances at voltages ranging from 5 to 13 kV. This is reduced to 120, 240, or 480 V for safety at the individual user site.

Glencoe Physics: Principles and Problems, Student Edition
Glencoe Physics: Principles and Problems, Student Edition
1st Edition
ISBN:9780078807213
Author:Paul W. Zitzewitz
Publisher:Paul W. Zitzewitz
Chapter25: Electromagnetic Induction
Section: Chapter Questions
Problem 65A
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 Transformers
• Explain how a transformer works.
• Calculate voltage, current, and/or number of turns given the other quantities.

23.7 Transformers Transformers do what their name implies-they transform voltages from one value to another (The term voltage is used rather than emf, because transformers have internal resistance). For example, many cell phones, laptops, video games, and power tools and small appliances have a transformer built into their plug-in unit (like that in Figure 23.26) that changes 120 V or 240 V AC into whatever voltage the device uses. Transformers are also used at several points in the power distribution systems, such as illustrated in Figure 23.27. Power is sent long distances at high voltages, because less current is required for a given amount of power, and this means less line loss, as was discussed previously. But high voltages pose greater hazards, so that transformers are employed to produce lower voltage at the user's location. Figure 23.26 The plug-in trancformer has become increacingly familiar with the proliferation of electronic devices that operate on voltages other than common 120 V AC. Mast are in the 3 to 12 V range. (credit: Shop Xtreme) 400 kV 13 kV 12 kV 240 V Power plant Step-up transformer High-voltage transmission line Step-down transformer (substation) Step-down transformer Figure 23.27 Transformers change voltages at several points in a power distribution system. Electric power is usually generated at greater than 10 kV, and transmitted long distances at voltages over 200 kV-sometimes as great as 700 kV-to limit energy lasses. Local power distribution to neighborhoods or industries goes through a substation and is sent short distances at voltages ranging from 5 to 13 kV. This is reduced to 120, 240, or 480 V for safety at the individual user site.
Transcribed Image Text:23.7 Transformers Transformers do what their name implies-they transform voltages from one value to another (The term voltage is used rather than emf, because transformers have internal resistance). For example, many cell phones, laptops, video games, and power tools and small appliances have a transformer built into their plug-in unit (like that in Figure 23.26) that changes 120 V or 240 V AC into whatever voltage the device uses. Transformers are also used at several points in the power distribution systems, such as illustrated in Figure 23.27. Power is sent long distances at high voltages, because less current is required for a given amount of power, and this means less line loss, as was discussed previously. But high voltages pose greater hazards, so that transformers are employed to produce lower voltage at the user's location. Figure 23.26 The plug-in trancformer has become increacingly familiar with the proliferation of electronic devices that operate on voltages other than common 120 V AC. Mast are in the 3 to 12 V range. (credit: Shop Xtreme) 400 kV 13 kV 12 kV 240 V Power plant Step-up transformer High-voltage transmission line Step-down transformer (substation) Step-down transformer Figure 23.27 Transformers change voltages at several points in a power distribution system. Electric power is usually generated at greater than 10 kV, and transmitted long distances at voltages over 200 kV-sometimes as great as 700 kV-to limit energy lasses. Local power distribution to neighborhoods or industries goes through a substation and is sent short distances at voltages ranging from 5 to 13 kV. This is reduced to 120, 240, or 480 V for safety at the individual user site.
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