POWER SOURCE

All electric and electronic products require power to work.
The source of power can be from
  • Main supply
  • Batteries
  • Photovoltaic Cells / Solar Panels
Main Supply
The main supply has a Alternating Current (A.C), it looks like Fig.1 below




This means the flow of electricity continuously changes in direction.
Singapore main voltage is 240 V(voltage) at 50 Hz.
The 50Hz is the frequency  of the electrical power supply. It means it changes direction of the current at 50 times per second.

Batteries
Batteries provides a Direct Current (D.C) supply.  A direct current only flows in one direction.  Direct current flows from the Positive terminal of a battery to the Negative terminal.

Batteries have a positive pole "+" and negative pole "-". When the two poles are connected in a closed
circuit, current will flow.

Batteries provides an electrical pressure to force electrons to move around a circuit.  This electrical pressure is called Potential Difference.
The units of measurement is Volts (V). The higher the voltage, the greater the pressure. Some of the common batteries that you may have come across are shown below.






Batteries can be connected in Series or Parallel. 
  • When two batteries are connected in series, the total voltage of the circuit is the sum of the voltage of the two batteries.
  • If a battery is added in parallel with another battery of the same voltage, the voltage remains unchanged.

Photovoltaic Cells / Solar Panels
It is another type of power supply that is Environmental friendly.  It is used to convert light energy to electricity energy. The light energy comes from our Sun. 
These panels are installed in open and unobstructed areas to receive maximum light energy.