 
 <prompt> Wetin dem dey use dielectrics for? Based on di question wey dey above, write one context wey contain di answer. E fit be 1 - 20 sentences. Context: <response>: Most types of capacitor get dielectric spacer wey dey increase their capacitance. Dis dielectrics dey mostly be insulators. But low capacitance devices dey wey get vacuum between their plates, wey allow dem operate for extremely high voltage and low losses. Variable capacitors wey get their plates open to the atmosphere dey common for radio tuning circuits. Later designs dey use polymer foil dielectric between the moving and stationary plates, with no significant air space between dem. 