A LED is a forward biased P-N junction diode which emits visible light when energized.

A light-emitting diode (LED) is a semiconductor light source. LEDs are used as indicator lamps in many devices and are increasingly used for other lighting. Introduced as a practical electronic component in 1962, early LEDs emitted low-intensity red light, but modern versions are available across the visible, ultraviolet, and infrared wavelengths, with very high brightness.

1) The main purpose of the capacitor is to store charge . If an instantanous strong current is to be flown in a circuit,the best way would be to connect the terminals of the circuit to a charge capacitor

2 A capacitor can store electric energy when disconnected from its charging circuit, so it can be used like a temporary battery. Capacitors are commonly used in electronic devices to maintain power supply while batteries are being changed. (This prevents loss of information in volatile memory.)

Force on a conductor in presence of an electric field
In presence of an electric field this surface charge will experience a force. If we consider a small area element of the surface of the conductor then force acting on area element is given by