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Help e Edit View History Bookmarks Window session.masteringphysics.com signed in as Brandon Chin : Heb : C PHY 2054.0002 Physics 2 Colwell 24my Problem 24.40 s previous| 12 of 19 Inext Problem 24.40 Part A What current would it need to carry in order to experience a very modest 1.0 x 10-3 N·m torque? Express your answer with the appropriate units. People have proposed driving motors with the earth's magnetic field. This is possible in principle, but the small field means that unrealistically large currents are needed to produce noticeable torques Suppose a 10-cm-diameter loop of wire is oriented for maximum torque in the earth's field. 1 = 17054-JA 1=1705.4 A Submit My Answers Give Up Incorrect; Try Again; 5 attempts remaining Continue 104-3) p10(-2) current 65-10-4(6) current 490 A

Explanation / Answer

torque in a current carrying coil is given by T=N*B*I*A*sin(theta)

hence its maximum value=N*B*I*A

where N=number of turns

B=magnetic field

I=current in the coil

A=area of the coil

given that N=1

B=earth's magnetic field=54 micro tesla=65*10^(-6) T

A=pi*0.25*diameter^2=7.854*10^(-3) m^2

then given that Toruqe =T=10^(-3)

hence 10^(-3)=1*65*10^(-6)*I*7.854*10^(-3)

==>I=1958.825 A

hence current in the coil required is 1958.825 A.

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