Most types of capacitor include a dielectric spacer, which increases their capacitance. These dielectrics are most often insulators. However, low capacitance devices are available with a vacuum between their plates, which allows extremely high voltage operation and low losses. Variable capacitors with their plates open to the atmosphere were commonly used in radio tuning circuits. Later designs use polymer foil dielectric between the moving and stationary plates, with no significant air space between them. COUNT 5
QSN1 What do many capacitors contain that raises the capacitance? ANS1 a dielectric spacer QSN2 What sort of dielectric is used in low capacitance devices? ANS2 a vacuum QSN3 What sort of capacitors have traditionally been used in radio tuning circuits? ANS3 Variable capacitors QSN4 How did the capacitor traditionally used in radio tuning circuits change over time?  ANS4 use polymer foil dielectric between the moving and stationary plates QSN5 What did the later designs of capacitors used in radio tuning circuits no longer have? ANS5 no significant air space