Which is TRUE about magnetic field lines? a) The begin on south poles and end on

Question

Which is TRUE about magnetic field lines? a) The begin on south poles and end on north poles, the same way electric field lines begin and end on positive and negative charges. b) They from closed loops directed away form a north pole and toward a south pole. c) They form closed loops directed away from a north Pole and toward a south pole. d) They begin on north poles and end on south poles, the same way electric field lines begin and end on positive and negative charges. Figure 1 below shows a schematic representation of the experiment used to determine the charge to mass ratio (e/m) of the electron. The magnetic field produced by the Helmholtz coils is B = 0.00147 T (pointing out of the page) and the electron beam follows a counter clockwise trajectory or radius r = 0.0365 m. Figure 2 is a schematic of the "electron gun" used to accelerate the electrons. What value of the potential difference was used to accelerate electrons if the e/m ratio determined in the experiment is 1.74 middot 10^11 C/kg? a) 200 V b) 300 V c) 350V d) 250 V A long solenoid has 110 turns/cm and carries current i. An electron moves within the solenoid in a circle of radius 2.61 cm perpendicular to the solenoid axis. The speed of the electron is 0.0416c (c = speed of light, equal to 2.998 times 10^8 m/s). Find the current i in the solenoid. a) 0.197 A b) 0.285 A c) 0.125 A d) 0.568 A

Explanation / Answer

16) The magnetic field lines form close loops directed away from a north pole and towards a south pole.

So option b) TRUE.

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