#  Fields of Moving Charges 

 



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###  Maltese Cross CRT

 \[M | t | ★★★\]  
Maltese cross obstacle and fluorescing glass show that electrons in a Crookes tube travel in straight lines and are affected by magnetic fields.  
\[[In-Depth Description](/presentations/maltese-cross-crt)\]

###  Cathode Ray Deflection

 \[M | t | ★★★★\]  
Small Crookes tube with built-in fluorescent screen shows electron beam deflection by magnetic field.  
\[[In-Depth Description](/presentations/cathode-ray-deflection)\]

###  TV Image Deflection

 \[L | t+ | ★★\]  
Image on *black and white* television is deflected by a magnet, not unlike the Maltese Cross.  
\[[In-Depth Description](/presentations/tv-image-deflection)\]

###  Flicker Bulb

 \[M | t | —\]  
A magnet placed near this commercially available light bulb causes the filament to vibrate at 60 Hz, producing a "flickering" effect.

###  e/m Apparatus

 \[L | t+ | —\]  
An electron beam is deflected into circular or spiral paths by a magnetic field.

###  Force Between Parallel Conductors

 \[L | t | ★★★★\]  
A strong surge of current from a 12V truck battery causes parallel wires to exert a force on each other.

###  Jumping Wire

 \[L | t+ | ★★★\]  
Motor effect on conductor between poles of horseshoe magnet.  
\[[In-Depth Description](/presentations/jumping-wire)\]

###  Boxtop Loudspeaker

 \[M | t+ | ★★★★\]  
Make a crude but effective loudspeaker from a cardboard box, coil of wire, and a magnet

###  Current Carrying Electrolyte

 \[S | t+ | —\]  
Electrolyte circulates in magnetic field.

###  Magnetohydrodynamic Propulsion

 \[M | t+ | ★★★\]  
Demonstrate how to propel a boat or submarine without moving parts.

###  Contact Us

 **Mailing Address**: Lecture Demonstration Services, Science Center, Rm B-08A, 1 Oxford Street, Cambridge, MA 02138  
**Campus Location**: Science Center B-08A | **Tel**: (617) 495-5824 | **Email**: scidemos-at-fas.harvard.edu