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Conceptual questions

What requirement for superconductivity makes current superconducting devices expensive to operate?

Very low temperatures necessitate refrigeration. Some materials require liquid nitrogen to cool them below their critical temperatures. Other materials may need liquid helium, which is even more costly.

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Name two applications for superconductivity listed in this section and explain how superconductivity is used in the application. Can you think of a use for superconductivity that is not listed?

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Problems

Consider a power plant is located 60 km away from a residential area uses 0-gauge ( A = 42.40 mm 2 ) wire of copper to transmit power at a current of I = 100.00 A . How much more power is dissipated in the copper wires than it would be in superconducting wires?

R copper = 0.24 Ω P = 2.377 × 10 3 W

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A wire is drawn through a die, stretching it to four times its original length. By what factor does its resistance increase?

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Digital medical thermometers determine temperature by measuring the resistance of a semiconductor device called a thermistor (which has α = −0.06 / ° C ) when it is at the same temperature as the patient. What is a patient’s temperature if the thermistor’s resistance at that temperature is 82.0% of its value at 37 ° C (normal body temperature)?

R = R 0 ( 1 + α ( T T 0 ) ) 0.82 R 0 = R 0 ( 1 + α ( T T 0 ) ) , 0.82 = 1 0.06 ( T 37 ° C ) , T = 40 ° C

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Electrical power generators are sometimes “load tested” by passing current through a large vat of water. A similar method can be used to test the heat output of a resistor. A R = 30 Ω resistor is connected to a 9.0-V battery and the resistor leads are waterproofed and the resistor is placed in 1.0 kg of room temperature water ( T = 20 ° C ) . Current runs through the resistor for 20 minutes. Assuming all the electrical energy dissipated by the resistor is converted to heat, what is the final temperature of the water?

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A 12-guage gold wire has a length of 1 meter. (a) What would be the length of a silver 12-gauge wire with the same resistance? (b) What are their respective resistances at the temperature of boiling water?

a. R Au = R Ag , ρ Au L Au A Au = ρ Ag L Ag A Ag , L Ag = 1.53 m ;
b. R Au,20 °C = 0.0074 Ω , R Au,100 °C = 0.0094 Ω , R Ag , 100 °C = 0.0096 Ω

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What is the change in temperature required to decrease the resistance for a carbon resistor by 10%?

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Additional problems

A coaxial cable consists of an inner conductor with radius r i = 0.25 cm and an outer radius of r o = 0.5 cm and has a length of 10 meters. Plastic, with a resistivity of ρ = 2.00 × 10 13 Ω · m , separates the two conductors. What is the resistance of the cable?

d R = ρ 2 π r L d r R = ρ 2 π L ln r o r i R = 2.21 × 10 11 Ω

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A 10.00-meter long wire cable that is made of copper has a resistance of 0.051 ohms. (a) What is the weight if the wire was made of copper? (b) What is the weight of a 10.00-meter-long wire of the same gauge made of aluminum? (c)What is the resistance of the aluminum wire? The density of copper is 8960 kg/m 3 and the density of aluminum is 2760 kg/m 3 .

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A nichrome rod that is 3.00 mm long with a cross-sectional area of 1.00 mm 2 is used for a digital thermometer. (a) What is the resistance at room temperature? (b) What is the resistance at body temperature?

a.
R 0 = 3.00 × 10 6 Ω ; b.
T c = 37.0 ° C R = 3.02 × 10 −6 Ω

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Questions & Answers

what is mutation
Janga Reply
what is a cell
Sifune Reply
how is urine form
Sifune
what is antagonism?
mahase Reply
classification of plants, gymnosperm features.
Linsy Reply
what is the features of gymnosperm
Linsy
how many types of solid did we have
Samuel Reply
what is an ionic bond
Samuel
What is Atoms
Daprince Reply
what is fallopian tube
Merolyn
what is bladder
Merolyn
what's bulbourethral gland
Eduek Reply
urine is formed in the nephron of the renal medulla in the kidney. It starts from filtration, then selective reabsorption and finally secretion
onuoha Reply
State the evolution relation and relevance between endoplasmic reticulum and cytoskeleton as it relates to cell.
Jeremiah
what is heart
Konadu Reply
how is urine formed in human
Konadu
how is urine formed in human
Rahma
what is the diference between a cavity and a canal
Pelagie Reply
what is the causative agent of malaria
Diamond
malaria is caused by an insect called mosquito.
Naomi
Malaria is cause by female anopheles mosquito
Isaac
Malaria is caused by plasmodium Female anopheles mosquitoe is d carrier
Olalekan
a canal is more needed in a root but a cavity is a bad effect
Commander
what are pathogens
Don Reply
In biology, a pathogen (Greek: πάθος pathos "suffering", "passion" and -γενής -genēs "producer of") in the oldest and broadest sense, is anything that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a germ. The term pathogen came into use in the 1880s.[1][2
Zainab
A virus
Commander
Definition of respiration
Muhsin Reply
respiration is the process in which we breath in oxygen and breath out carbon dioxide
Achor
how are lungs work
Commander
where does digestion begins
Achiri Reply
in the mouth
EZEKIEL
what are the functions of follicle stimulating harmones?
Rashima Reply
stimulates the follicle to release the mature ovum into the oviduct
Davonte
what are the functions of Endocrine and pituitary gland
Chinaza
endocrine secrete hormone and regulate body process
Achor
while pituitary gland is an example of endocrine system and it's found in the Brain
Achor
what's biology?
Egbodo Reply
Biology is the study of living organisms, divided into many specialized field that cover their morphology, physiology,anatomy, behaviour,origin and distribution.
Lisah
biology is the study of life.
Alfreda
Biology is the study of how living organisms live and survive in a specific environment
Sifune
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Source:  OpenStax, University physics volume 2. OpenStax CNX. Oct 06, 2016 Download for free at http://cnx.org/content/col12074/1.3
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