Welcome to practical physicsPracticle physics - practical activities designed for use in the classroom with 11 to 19 year olds
 

Vibration generator to generate continuous waves

Vibration generator to generate continuous wavesApparatus and materials

Ripple tank and accessories
Rubber bands 
Sets of leads to motor 
Dippers 
Dry cells 
Rheostats

Technical notes

Power for the motor 
The motor works well from a 1.5 volt cell in series with a 12-ohm rheostat. Two cells may be needed for the higher speeds but the motor then goes rather fast with the rheostat set at its minimum value. The polarity of the battery determines the direction of rotation, but that is immaterial. (If a battery with a higher e.m.f. is used, a rheostat with a correspondingly high resistance would be required.) 
 
Some manufacturers supply special power units for use with the ripple tanks. These provide the necessary voltage for the lamps and also a variable voltage output to drive the motors. They avoid the need for a transformer to light the lamp and a separate supply for the motors and some teachers may prefer to use them despite the extra cost.