PASCO SE-9638 Instruction Manual And Experiment Manual Download Page 9

4

e/m Apparatus

012-03471E

!

where:
V = the accelerating potential
a = the radius of the Helmholtz coils
N = the number of turns on each Helmholtz coil = 130

µ

0

 = the permeability constant = 4

þ

 x 10

-7

I = the current through the Helmholtz coils
r = the radius of the electron beam path

Deflections of Electrons in an Electric
Field

IMPORTANT:

  Do not leave the beam on for long

periods of time in this mode. The beam will
ultimately wear through the glass walls of the tube.

You can use the deflection plates to demonstrate how the
electron beam is deflected in an electric field.
1. Setup the equipment as described above for measuring

e/m except:
a. Flip the toggle switch to ELECTRICAL DEFLECT.
b. Do not supply current to the Helmholtz coils.
c. Connect a 0-50 VDC power supply between the

banana plug connectors labeled DEFLECT PLATES
(UPPER and LOWER).

2. Apply the 6.3 (VDC or VAC), or voltage noted on tube,

to the HEATER and 150-300 VDC to the ELEC-
TRODES of the ELECTRON GUN (the accelerating
potential). Wait ten minutes to warm up the cathode.

3. When the electron beam appears, slowly increase the

voltage to the deflection plates from 0 V to
approxmately 50 VDC. Note the deflection of the
electron beam. Note that the beam is bent towards the
positively charged plate.

Two Simple Demonstrations

1. Instead of using the Helmholtz coils to bend the electron

beam, you can use a permanent magnet to show the
effect of a magnetic field on the electron beam. Just
provide the following power to the e/m apparatus:
HEATER:  6.3 (VAC or VDC), or voltage noted on tube
ELECTRON GUN ELECTRODES: 150- 300 VDC
When the electron beam appears, use your permanent
magnet to bend the beam.

2. The socket for the e/m tube is designed so that the tube

can be rotated 90 degrees. The tube can therefore be
oriented so it is at any angle, from 0-90 degrees, with
respect to the magnetic field from the Helmholtz coils.
By setting up the equipment as for measuring e/m, you
can rotate the tube and study how the beam deflection is
affected.

Summary of Contents for SE-9638

Page 1: ...1 234 05 1 6 78 6669 9 0 0 2 AA BACD9 1 E C AA F G3 5 0 HI3 7 J 6 K Instruction Manual and Experiment Guide for the PASCO scientific Model SE 9638 Includes Teacher s Notes and Typical Experiment Results e m APPARATUS ...

Page 2: ...e m Apparatus 012 03471E Discard This Page ...

Page 3: ...Copyright Warranty and Equipment Return ii Introduction 1 Equipment 1 Operation Measuring e m 2 Analysis of e m Measurement 3 Deflections of Electrons in an Electric Field 4 Two Simple Demonstrations 4 Diagram of Connections 5 Improving Experimental Results 6 ...

Page 4: ...r the units must be packed properly Carriers will not accept responsibility for damage caused by improper packing To be certain the unit will not be damaged in shipment observe the following rules 1 The carton must be strong enough for the item shipped 2 Make certain there is at least two inches of packing material between any point on the apparatus and the inside walls of the carton 3 Make certai...

Page 5: ...u can t call PASCO right away you won t lose valuable data If possible have the apparatus within reach when calling This makes descriptions of individual parts much easier If your problem relates to the instruction manual note Part number and Revision listed by month and year on the front cover Have the manual at hand to discuss your questions Feed Back If you have any comments about this product ...

Page 6: ...egrees with respect to the magnetic field from the Helmholtz coils You can therefore rotate the tube and examine the vector nature of the magnetic forces on moving charged particles Other experiments are also possible with e m tube Helmholtz coils Controls Figure 1 The e m Apparatus Equipment the e m tube For example you can use a small permanent magnet instead of the Helmholtz coils to investigat...

Page 7: ...re accelerat ing potential such as the PASCO Model SB 9624 Multimeter Operation Measuring e m 1 If you will be working in a lighted room place the hood over the e m apparatus 2 Flip the toggle switch up to the e m MEASURE position 3 Turn the current adjust knob for the Helmholtz coils to the OFF position 4 Connect your power supplies and meters to the front panel of the e m apparatus as shown in F...

Page 8: ...arge of the electron Since the electrons are moving in a circle they must be experiencing a centripetal force of magnitude Fc mv2 r 2 where m is the mass of the electron v is its velocity and r is the radius of the circular motion Since the only force acting on the electrons is that caused by the magnetic field Fm Fc so equations 1 and 2 can be combined to give evB mv2 r or e m v Br 3 Therefore in...

Page 9: ... HEATER and 150 300 VDC to the ELEC TRODES of the ELECTRON GUN the accelerating potential Wait ten minutes to warm up the cathode 3 When the electron beam appears slowly increase the voltage to the deflection plates from 0 V to approxmately 50 VDC Note the deflection of the electron beam Note that the beam is bent towards the positively charged plate Two Simple Demonstrations 1 Instead of using th...

Page 10: ...eater Grid Anode Deflection Plates e m Tube Cathode Power Supply Heater Voltage 150 300 VDC Focus Adjust Variable Resistor Slide Toggle Switch e m MEASURE ELECTRICAL DEFLECT Upper Lower BLK BLK WHT YEL BLK ORG ORG WHT RED ORG 15K 15W 5K 5 ý BLK BLK BLU pin 1 pin 2 pin 6 pin 10 YEL pin 12 pin 11 Diagram of Connections for the SE 9638 e m Apparatus ...

Page 11: ... due to this lost electron velocity measure radius to the outside of the beam path 3 To minimize the relative effect of collisions keep the accelerating voltage as high as possible Above 250V for best results Note however that if the voltage is too high the radius measurement will be distorted by the curvature of the glass at the edge of the tube Our best results were made with radii of less than ...

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