Magnetic Fields - Structured Questions
Q1. Here is a diagram of a mass spectrometer
(a) The magnetic field strength in the velocity selector is 0.14T and the electric field strength is 20 kVm–1.
(i) Define the unit for magnetic flux density, the tesla.
(2 marks)
(ii) Show that the velocity selected is independent of the charge on an ion.
(2 marks)
(iii) Show that the velocity selected is about 140 kms–1
(1 mark)
(b) A sample of nickel is analysed in the spectrometer. The two most abundant isotopes of nickel are:
and 
Each ion carries a single charge of +1.6 × 10–19 C
The Ni-58 ion strikes the photographic plate 0.28 m from the point P at which the ion beam enters the ion separator.
Calculate:
(i) the magnetic flux density of the field in the ion separator;
(3 marks)
(ii) the separation of the positions where the two isotopes hit the photographic plate.
(2 marks)
(Total 10 marks)
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