The subprime mortgage crisis was caused by hedge funds, banks, and insurance companies. The first two created mortgage-backed securities. The insurance companies covered them with credit default swaps. Demand for mortgages led to an asset bubble in housing.
The field of dielectrics is a branch of physics that covers how insulating materials separate different electrical charges in a capacitor. A capacitor is a device with two metal plates of opposite charges, with a dielectric insulating material in between the keeps the charges separate.
A capacitor is a passive electronic component which basically consist of two parallel metal layers separated by an insulator. The types of capacitors are named after this dielectric. We use capacitors with dielectrics made of ceramic, mica, polyester, tantalum etc. Capacitors are used to block or to store voltages and to filter out signals.