Academic Integrity: tutoring, explanations, and feedback — we don’t complete graded work or submit on a student’s behalf.

J. J. Thomson is best known for his discoveries about the nature of cathode rays

ID: 1259861 • Letter: J

Question

J. J. Thomson is best known for his discoveries about the nature of cathode rays. His other important contribution was the invention, together with one of his students, of the mass spectrometer, a device that measures the ratio of mass m to (positive) charge qof an ion.

After being accelerated to a speed of 1.03

J. J. Thomson is best known for his discoveries about the nature of cathode rays. His other important contribution was the invention, together with one of his students, of the mass spectrometer, a device that measures the ratio of mass m to (positive) charge qof an ion. After being accelerated to a speed of 1.03?105m/s , the particle enters a uniform magnetic field of strength 0.700T and travels in a circle of radius 30.0cm (determined by observing where it hits the screen as shown in the figure). The results of this experiment allow one to find m/q. Find the ratio m/q for this particle. Express your answer numerically in kilograms per coulomb.

Explanation / Answer

We know that
           radius of the path r = m v / qB
                       ==>        m / q = B r /v
                                               = 0.70 * 0.30 / 1.03 x 105
                                               = 0.2039 x 10-5 kg / C
                                               = 2.039 *10^-6 kg/C