1. You wish to make a mass spectrometer with a chamber 46cm on a side. a. How la

ID: 1320295 • Letter: 1

Question

1. You wish to make a mass spectrometer with a chamber 46cm on a side.

a. How large a magnetic field is needed to keep singly ionized helium atoms (4He ) with kinetic energy 270eV within the chamber?

Express your answer to two significant figures and include the appropriate units.

2. A 12cm diameter circular wire loop carries a current of 2.8A .

a. Find the torque on the loop in a 1.5T magnetic field directed perpendicular to the loop.

b. Find the torque on the loop in a 1.5T magnetic field directed in the plane of the loop.

Express your answer to two significant figures and include the appropriate units.

Part 1)

KE = 270 eV

To get to Joules, multiply by 1.6 X 10-19 = 4.32 X 10-17 J

KE = .5mv2

The mass of the He Atom = 4.0026 amu where 1 amu is 1.6605 X 10-27 kg

Thus mass is 6.646 X 10-27 kg

4.32 X 10-17 = .5(6.646 X 10-27)(v2)

v = 1.14 X 105 m/s

r = mv/qB

(.23) = (6.646 X 10-27)(1.14 X 105)/(1.6 X 10-19)(B)

B = .021 T

Part 2a)

Torque = BIA

Torque = (1.5)(2.8)(pi)(.06)2

Torque = .048 Nm

Part 2b)

There is ZERO area through which the magnetic field will flow when the field is in the plane of the loop

Torque = 0 Nm

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