Un capacitor de placas paralelas separadas por aire, de 5.8 μF, tiene una separacion de 5 mm y esta cargado a una diferencia de potencial de 400 V .
(a) Calcule la energia potencial y densidad de energıa almacenada entre las placas.
(b) Si se inserta un dielectrico con K = 2.7 entre las placas del capacitor, cual es ahora la energıa potencial
y densidad de energıa almacenada?.

Sally turns on her cellular telephone to speak to her friend who is located thousands of miles away. which of the following best describes how such a telephone is able to transmit and receive information? a. the cellular telephone transmits, receives, and encodes information using only sound waves. b. the cellular telephone transmits, receives, and encodes information using only electromagnetic waves. c. the cellular telephone transmits information by electromagnetic waves to a receiver which then encodes them and produces sound. d. the cellular telephone transmits information by sound waves to a receiver which then encodes them and produces electromagnetic waves.