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An example of magnetohydrodynamics (MHD) comes from the flow of a river (salty water). This fluid interacts with the Earth’s magnetic field to produce a potential difference between the two river banks. How would you go about calculating the potential difference?

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Draw gravitational field lines between 2 masses, electric field lines between a positive and a negative charge, electric field lines between 2 positive charges and magnetic field lines around a magnet. Qualitatively describe the differences between the fields and the entities responsible for the field lines.

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Problems&Exercises

Indicate whether the magnetic field created in each of the three situations shown in [link] is into or out of the page on the left and right of the current.

Figure a shows current I running from bottom to top. Figure b shows an electron moving with velocity v from bottom to top. Figure c shows current I running from top to bottom.

(a) right-into page, left-out of page

(b) right-out of page, left-into page

(c) right-out of page, left-into page

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What are the directions of the fields in the center of the loop and coils shown in [link] ?

Figure a shows current in a loop, running counterclockwise. Figure b shows current in a coil running from left to right. Figure c shows current in a coil running from right to left.
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What are the directions of the currents in the loop and coils shown in [link] ?

Figure a shows the magnetic field into the page in the middle of a loop. Figure b shows the magnetic field within a coil running from left to right. Figure c shows B running from right to left within a coil.

(a) clockwise

(b) clockwise as seen from the left

(c) clockwise as seen from the right

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To see why an MRI utilizes iron to increase the magnetic field created by a coil, calculate the current needed in a 400-loop-per-meter circular coil 0.660 m in radius to create a 1.20-T field (typical of an MRI instrument) at its center with no iron present. The magnetic field of a proton is approximately like that of a circular current loop 0 . 650 × 10 15 m in radius carrying 1 . 05 × 10 4 A size 12{1 "." "05" times "10" rSup { size 8{4} } `A} {} . What is the field at the center of such a loop?

1 . 01 × 10 13 T size 12{1 "." "01" times "10" rSup { size 8{"13"} } " T"} {}

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Inside a motor, 30.0 A passes through a 250-turn circular loop that is 10.0 cm in radius. What is the magnetic field strength created at its center?

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Nonnuclear submarines use batteries for power when submerged. (a) Find the magnetic field 50.0 cm from a straight wire carrying 1200 A from the batteries to the drive mechanism of a submarine. (b) What is the field if the wires to and from the drive mechanism are side by side? (c) Discuss the effects this could have for a compass on the submarine that is not shielded.

(a) 4 . 80 × 10 4 T size 12{4 "." "80" times "10" rSup { size 8{ - 4} } `T} {}

(b) Zero

(c) If the wires are not paired, the field is about 10 times stronger than Earth’s magnetic field and so could severely disrupt the use of a compass.

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How strong is the magnetic field inside a solenoid with 10,000 turns per meter that carries 20.0 A?

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What current is needed in the solenoid described in [link] to produce a magnetic field 10 4 size 12{"10" rSup { size 8{4} } } {} times the Earth’s magnetic field of 5 . 00 × 10 5 T size 12{5 "." "00" times "10" rSup { size 8{ - 5} } `T} {} ?

39.8 A

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How far from the starter cable of a car, carrying 150 A, must you be to experience a field less than the Earth’s ( 5 . 00 × 10 5 T ) ? size 12{ \( 5 "." "00" times "10" rSup { size 8{ - 5} } `T \) ?} {} Assume a long straight wire carries the current. (In practice, the body of your car shields the dashboard compass.)

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Measurements affect the system being measured, such as the current loop in [link] . (a) Estimate the field the loop creates by calculating the field at the center of a circular loop 20.0 cm in diameter carrying 5.00 A. (b) What is the smallest field strength this loop can be used to measure, if its field must alter the measured field by less than 0.0100%?

(a) 3 . 14 × 10 5 T size 12{3 "." "14" times "10" rSup { size 8{ - 5} } `T} {}

(b) 0.314 T

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Questions & Answers

how does Neisseria cause meningitis
Nyibol Reply
what is microbiologist
Muhammad Reply
what is errata
Muhammad
is the branch of biology that deals with the study of microorganisms.
Ntefuni Reply
What is microbiology
Mercy Reply
studies of microbes
Louisiaste
when we takee the specimen which lumbar,spin,
Ziyad Reply
How bacteria create energy to survive?
Muhamad Reply
Bacteria doesn't produce energy they are dependent upon their substrate in case of lack of nutrients they are able to make spores which helps them to sustain in harsh environments
_Adnan
But not all bacteria make spores, l mean Eukaryotic cells have Mitochondria which acts as powerhouse for them, since bacteria don't have it, what is the substitution for it?
Muhamad
they make spores
Louisiaste
what is sporadic nd endemic, epidemic
Aminu Reply
the significance of food webs for disease transmission
Abreham
food webs brings about an infection as an individual depends on number of diseased foods or carriers dully.
Mark
explain assimilatory nitrate reduction
Esinniobiwa Reply
Assimilatory nitrate reduction is a process that occurs in some microorganisms, such as bacteria and archaea, in which nitrate (NO3-) is reduced to nitrite (NO2-), and then further reduced to ammonia (NH3).
Elkana
This process is called assimilatory nitrate reduction because the nitrogen that is produced is incorporated in the cells of microorganisms where it can be used in the synthesis of amino acids and other nitrogen products
Elkana
Examples of thermophilic organisms
Shu Reply
Give Examples of thermophilic organisms
Shu
advantages of normal Flora to the host
Micheal Reply
Prevent foreign microbes to the host
Abubakar
they provide healthier benefits to their hosts
ayesha
They are friends to host only when Host immune system is strong and become enemies when the host immune system is weakened . very bad relationship!
Mark
what is cell
faisal Reply
cell is the smallest unit of life
Fauziya
cell is the smallest unit of life
Akanni
ok
Innocent
cell is the structural and functional unit of life
Hasan
is the fundamental units of Life
Musa
what are emergency diseases
Micheal Reply
There are nothing like emergency disease but there are some common medical emergency which can occur simultaneously like Bleeding,heart attack,Breathing difficulties,severe pain heart stock.Hope you will get my point .Have a nice day ❣️
_Adnan
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Innocent
I think infection prevention and control is the avoidance of all things we do that gives out break of infections and promotion of health practices that promote life
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Heyy Lubega hussein where are u from?
_Adnan
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ESTHER Reply
Many sites of the body have it Skin Nasal cavity Oral cavity Gastro intestinal tract
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skin
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skin,Oral,Nasal,GIt
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part of a tissue or an organ being wounded or bruised.
Wilfred
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Binomial nomenclature
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Source:  OpenStax, College physics for ap® courses. OpenStax CNX. Nov 04, 2016 Download for free at https://legacy.cnx.org/content/col11844/1.14
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