What is the source of electricity?

Answer 1

An electric current is a movement of electric charges through a material known as a conductor. In the case of metal conductors, these electric charges are called 'free electrons', which are negatively charged.

In the case of 'direct current' (d.c.) the direction of current is in one direction whereas, in the case of 'alternating current' (a.c.), the direction of current continuously reverses.

Electric charges flow as a result of a 'potential difference' (or 'voltage') applied across opposite ends of the conductor. In simple terms, a potential difference exists when the amount of negative charge at one end of the conductor is different from the amount of negative charge at the opposite end. We describe the 'less negative charge' as being 'positive, with respect to' the more-negative charge.

In metal conductors, the electrons already within the conductor are repelled from the end which is more negative, towards the end which is less negative ('positive') and, so, travel along the length of the conductor. In the case of an a.c. current, this potential difference is continually reversing direction, causing the resulting current to reverse direction in step with the potential difference.

Sources of d.c. potential difference (not 'of current') include batteries, d.c. generators, photovoltaic devices, piezoelectric devices, etc. The main source of a.c. potential difference is the a.c. generator, also known as an 'alternator'.

Because it's possible to easily and efficiently alter the voltage level of a.c., using machines called 'Transformers', electricity generation/transmission/distribution systems are practically always a.c. systems.

Although electrons move from negative to positive, you may be surprised to hear 'current' being described as moving 'from positive to negative'. This (incorrect) 'direction' dates from the 1800s, when the nature of the atom and, therefore, electrons, was unknown. In those days, an electric current was thought to be some form of mysterious 'fluid' that flowed from 'high pressure' ('positive') to 'low pressure' ('negative'). As many subsequent 'rules' (such as for the direction of electromagnetic fields) depend upon knowing current direction, many textbooks prefer to use this (incorrect) direction, which we now call 'conventional flow' (or 'Franklinian flow', named in honour of Benjamin Franklin, whose research led to this idea), rather than change the subsequent rules.

So you must be aware that some textbooks use 'electron flow' (- to +) to describe current direction, whereas others use 'conventional flow' (+ to -) to describe current direction. Knowing which 'current' direction is used is important, as it affects the rules used to determine electromagnetic fields.

Answer 2

power generators or nuclear power can be used to make electricity

Answer 3

protons and electrons
Electrons.

Answer 4

protons and electrons.