Charged Particles

Which line, A to D, correctly describes the trajectory of charged particles which enter, at right angles, (a) a uniform electric field, and (b) a uniform magnetic field?

• A

• B

• C

• D

Protons, each of mass m and charge e, follow a circular path when travelling perpendicular to a magnetic field of uniform flux density B. What is the time taken for one complete orbit?

• 2πeB/m

• m/2πeB

• eB/2πm

• 2πm/eB

• 3.7

• 7.5

• 60

• 112.5

Particles of mass m carrying a charge Q travel in a circular path of radius r in a magnetic field of flux density B with a speed v. How many of the following quantities, if changed one at a time, would change the radius of the path?

m, Q, B, v

• one

• two

• three

• four

The path of electrons in a CRO follows the path shown above. Part of the path crosses a magnetic field.

In which one or more sections of the path does a magnetic field act on the electron?

• AB

• BC

• CD

• no part of the path

The shape of the path followed by electrons between B and C is best described by:

• a circular arc

• a parabolic path

• a hyperbolic path

• none of the option A, B and C

Which of the following best describes the path of an electron as it passes through the magnetic field?

• It is deflected to the left.

• It is deflected to the right.

• It is deflected up.

• It is deflected down.

Which of the following is closest to the speed of 10 keV electrons?

• 6*10⁷ ms^-1

• 7*10⁷ ms^-1

• 8*10⁷ ms^-1

• 9*10⁷ ms^-1

Which of the following is closest to the radius of curvature of 10keV electrons as they travel through a uniform magnetic field of strength 2.0 T?

• 2*10^-3 m

• 2*10^-4 m

• 2*10^-5 m

• 2*10^-7 m

As high-energy electrons pass through one of the bending magnets in a synchrotron, they are bent through an arc of radius 7.0 m. The magnetic field strength is 1.7 T. Which of the following is closest to the momentum of the electrons?

• 1*10^-18 Ns

• 2*10^-18 Ns

• 3*10^-18 Ns

• 4*10^-18 Ns