CURRENT

Atom consists of proton, neutron and electrons. An electron has negative electrical charge and  proton has a positive electrical charge. An atom “acquires a negative electrical charge when it gains an electron and a positive electrical charge when it loses an electron. An electron can move from one atom to another. Thus the flow of billions of microscopic electrons from one atom to another is called electric current.

The unit of electric current is Ampere. Ampere meter or ammeter is connected in series in the circuit to measure the current symbol A or is.

Electromotive Force - emf

Electromotive force is the potential difference across the two terminals of a voltage source when it is not connected to any circuit. Once it is connected to a circuit, the voltage reduces slightly because of the internal resistance of the voltage source. Unit Volts (Volts or V)


POTENTIAL DIFFERENCE

Potential difference between any two points In the electric field is defined as the amount of work done in moving a unit positive charge without acceleration from one point to another along any path between the two points. A volt meter is connected in parallel in the circuit to measure the potential difference.


RESISTANCE

The resistance that occurs when electricity flows through a conductor is called electrical resistance. The unit of resistance is 'ohm'. (simple Ω) . An ohm meter is connected to the conductor to measure the resistance.

Ohm's Law

Ohm’s law states that the voltage across a conductor is directly proportional to the current flowing through it, provided all physical conditions and temperatures remain constant.