Question

21.
Concept 26-7 gives the magnetic torque on a current loop with a single turn of wire.  To achieve higher torques suitable for practical applications, motors use coils of wire with several turns.  What is the maximum torque on a coil with 100 turns, area 9.0 × 10^-4 m², and current 2.0 A in the presence of a magnetic field of magnitude 0.2 T?   Express your answer in N·m.  
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24.
Mass spectrometers select particles of a particular velocity using perpendicular electric and magnetic fields for which the total electromagnetic force vanishes.  Sodium ions of charge +e move northward with a speed of 5.0 x 10⁴ m/s through a uniform magnetic field of 0.001 T, directed eastward.  What is the magnitude and direction of the uniform electric field for which the total electromagnetic force on these ions is zero?  

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5.0 x 10⁷ V/m, directed vertically upward.

50 V/m, directed vertically upward.

50 V/m, directed vertically downward.

 

Answer 1

21.

torque is given by

T = N B A i

T = 100* 0.2* 2*9* 10^-4

T = 0.036 Nm

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