Kinetic

• By far the most common way to make electricity is by harnessing the motion of a machine. This is called kinetic energy. The part that makes the electricity is called a generator; in it, a wire coil spins inside a magnetic field, producing a current. Other machines, usually turbines, drive the generator. The turbines may be powered by steam, wind or falling water.
  
  

Thermal

• You can use a thermocouple to make small amounts of electricity directly from heat. Here, the temperature difference between two surfaces creates a voltage in a sandwich of two metals. Because they produce only milliwatts of power, they mainly see use as temperature gauges.
  
  

Nuclear

• In a nuclear power plant, the energy from radioactivity is used to heat water, which makes steam to drive a turbine and a generator. While this uses nuclear energy to make electricity, kinetic energy does the work. Nuclear batteries, on the other hand, create electricity directly from radioactive decay. Nuclear materials in the battery, such as americium, give off a stream of charged particles. This is used to make an electric current. Nuclear batteries are used for heart pacemakers and deep-space probes.
  
  

Chemical

• In a battery, chemical energy is used to create electricity. The energy comes from ions---charged molecules---uniting into a neutral compound. When the positive and negative terminals of the battery are connected to a circuit, the chemical energy in the ions becomes electrical energy. The chemicals in the battery determine its voltage; the amount determines its total capacity. When the chemicals are used up, the electricity stops. Rechargeable batteries let you reverse the reaction, creating "fresh" chemicals from the used-up supply. Creating electricity uses up the chemicals, regenerating the chemicals takes electricity.
  
  

Solar

• Photovoltaic (PV) cells convert light from the sun or other sources to electricity. Electrons in the PV cell, made of silicon, cadmium or other semiconductors, are mobilized by the energy of the light; this can be used as an electric current. Each cell can deliver several milliwatts of power; a typical solar panel for home use produces about 100 watts.