Physics: Principles with Applications (7th Edition)

Published by Pearson
ISBN 10: 0-32162-592-7
ISBN 13: 978-0-32162-592-2

Chapter 20 - Magnetism - Problems - Page 586: 53

Answer

69.7 microamperes.

Work Step by Step

We see from the equation for the deflection of the pointer for a galvanometer, section 20–10, that the deflection is proportional to the current multiplied by the magnetic field. The magnetic field changes to 0.760 times its original value, and the deflection of the needle is to remain the same. $$I_1B_1=I_2B_2$$ $$I_2= \frac{ I_1B_1}{B_2}=\frac{ (53.0\mu A)B_1}{0.760B_1}=69.7 \mu A $$ We see that the current increases by a factor of 1/0.760 to obtain the same deflection as before.
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