Practical Problem Solving in University Physics by Fung Albert

Author:Fung, Albert [Fung, Albert]
Language: eng
Format: epub
Published: 2021-07-09T00:00:00+00:00

50.​ Voltage on airplane

-

Q50: When an airplane flies in the air, the wingspan of 70 m pass through Earth magnetic field of 50 μT and generates an EMF (electromotive force) of 1 V. Find the airplane speed.

A50: With a conductor moving in a magnetic field,

motional EMF = v·L·B, where Length L = 70 m.

Magnetic field B = 50 x 10-6 T.

So, v = 286 m/s = 640 mph.

51.​ Car motor

-

Q51: In a sports car, the electric motor coil has 270 turns of area 12 cm x 15 cm. in a magnetic field of 0.6 T. The current in the coils is 30 A. The overall tire diameter is 70 cm. Find the:

(a) magnetic dipole moment in the coils.

(b) rolling friction on the ground, assuming all the torque goes to overcoming friction.

A51: Torque is provided by the electric motor.

The coils in the motor acts like a magnetic dipole with a moment μ = N·I·A, where N = 270 turns, I = 30 A, A = 12 cm x 15 cm = 0.018 m2 . So, μ = 146 N/T (a)

Torque τ = μ x B, where B = 0.6 T. So, τ = 87.5 N·m.

On the other hand, τ = r x F, where radius r = 70 cm / 2 = 35 cm.

So, rolling friction F = 250 N. ​ ​ (b)

Download

Copyright Disclaimer:
This site does not store any files on its server. We only index and link to content provided by other sites. Please contact the content providers to delete copyright contents if any and email us, we'll remove relevant links or contents immediately.