7. A Hall-effect probe operates with a 120 -mA current. When the probe is placed

Question

7. A Hall-effect probe operates with a 120 -mA current. When the probe is placed in a uniform magnetic field of magnitude 0.0900 T, it produces a Hall voltage of 0.780 µV.

(a) When it is used to measure an unknown magnetic field, the Hall voltage is 0.300 µV. What is the magnitude of the unknown field? ______mT

(b) The thickness of the probe in the direction of B is 1.60 mm. Find the density of the charge carriers, each of which has charge of magnitude e). ______m-3

6.A 46.0-turn circular coil of radius 5.20 cm can be oriented in any direction in a uniform magnetic field having a magnitude of 0.495 T. If the coil carries a current of 24.5 mA, find the magnitude of the maximum possible torque exerted on the coil.
______N · m

Explanation / Answer

VH = ( I B ) / (q n d )

so B is directlt propotional to VH,.

0.3 / 0.78 = B / (0.09)

B= 0.035 T Or 35 mT

b) 0.780 x 10^-6 = (0.120 x 0.09 ) / (1.6 x 10^-19 x n x 1.6 x 10^-3)

n = 5.41 x 10^25 per cubic meter

6. MAximum torque = N I A B

= 46 x (24.5 x 10^-3) x (pi x 0.052^2) x (0.495)

= 4.74 x 10^-3 N m

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