| E&M
> Magnetic Fields and Forces > Force on Moving Charges |
DCS#
5H30.20 |
e/m TUBE
-
APPARATUS
| e/m tube |
214A |
| Helmholtz coils |
214A |
| 5 kV DC power supply |
214A |
| 6.3 V transformer |
214-01-D |
| variac |
202-08-H |
| low voltage DC power supply |
214-01-C |
| video camera |
202 |
DESCRIPTION
- This can be used to show that a
magnetic field
perpendicular
to the electron beam deflects the beam along a
circular
path.
- Connect the
deflection
plates
to a DC power supply, adjust the voltage so the Coulomb force on the
electrons
balances the magnetic force, and determine e/m.
- NOTES
Helmholtz
coils: Connect jacks labeled "Z" on
Helmholtz coils
to each other. Connect those marked "A" to the low voltage DC
power
supply.
- Filament voltage: Connect
6.3 V transformer to the jacks at back of tube. Plug the
transformer into
the variac. Turn the variac up to about 65. Light should
be seen coming from the filament. Do not exceed 6 V to the
filament.
Accelerating
voltage: Connect the 5 kV DC supply to the jack at the back of
tube and
the jack
along neck of tube which goes to the anode of the electron gun.
Turn the accelerating voltage up to about 2 kV.
- Vary the current to Helmholtz coils
to
show deflection
of the electron beam.