Question 1

Paper 2Medium12 marks

A beam of protons passes through a velocity selector and then enters a region containing a uniform magnetic field. Figure 1 shows the arrangement. The diagrams are schematic and not to scale. The protons pass undeflected through the selector.

uniform magnetic field,B1=0.040 T, into the pageuniform magnetic field,B2=0.50 T, into the page××××××××+240 V0 Vproton beam1.00 cm××××××××××××××××××××PQCr=1.25 cm
(a)

Calculate the magnitude of the electric field between the plates in region 1.

[2]
(b)

Consider the motion of the protons in region 1.

(i)

If the magnetic field in region 1 is switched off, state the direction of the acceleration of the protons while they are between the plates.

[1]
(ii)

Determine the speed of the protons that pass undeflected through the selector.

[2]
(c)

Use the path in region 2 to determine the charge-to-mass ratio of a proton.

[3]
(d)

Explain why the kinetic energy of a proton remains constant as it moves through region 2.

[2]
(e)

The speed of the protons entering region 2 is increased to 1.501.50 times its original value. Using your result from (c), determine the new radius of their path in region 2.

[2]

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