A magnetic field is used to suspend wire of mass 0.02 kg and length 0.15 m. The

Question

A magnetic field is used to suspend wire of mass 0.02 kg and length 0.15 m. The wire is caring current of 10A. What is the magnetic field magnitude that can balance the pull of gravity? Basic source of magnetism is: A. Static charged particles B. Movement of charged particles C. Magnetic dipoles D. Magnetic domains Problem A particle of mass 3 times 10^-2 kg and charge of +5mu C enters a region of space where there is magnetic field of 1 T that is perpendicular to the velocity of the particle. When the particle encounters the magnetic field, it experience an acceleration of 12 m/s^2. What is the speed of the particle when it enters the magnetic field region? A bar magnet is divided in two pieces. Which of the following statements is true? A. The bar magnet is demagnetized. B. The magnetic field of each separated piece becomes stronger. C. The magnetic poles are separated. D. Two new bar magnets are created. E. The electric field is created An inductor is connected to the terminals of a battery that has an emf of 12.0 V and negligible internal resistance The current is 4.86 mA at 0.725 ms after the connection is completed. After a long time the current is 6.45 mA. What are (a) the resistance of the inductor, (b) inductance of the inductor? Ferro magnets contain all of the following except: A. Gold B. Iron C. Nickel D. Cobalt

Explanation / Answer

1 )

using equation

B i L = m g

B = m g / i L

B = 0.02 X 9.8 / 10 X 0.15

B = 0.13 T

2)

using V = m a / B q sin90

V = 3 X 10-2 X 12 / 1 X 5 X 10-6 X 1

V = 72000 m/sec

3 )

a )

R = 12 / 6.45 X 10-3  

R = 1860.46 Ohm

b )

i = imax ( 1 - exp ( - R t / L ) )

4.86 X 10-3 = 6.45 X 10-3 X ( 1 - exp ( 0.725 X 10-3 X 1860.46 / L ) )

0.753 = ( 1 - exp ( 0.725 X 10-3 X 1860.46 / L ) )

L = 0.96 H

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