# emf – potential difference – current – power – energy : What Is ? with SI units

This article all about what is Electromotive force (EMF), Potential Difference, Current, Power Energy in the electrical circuit of basic electrical engineering .

## Definition And Details Of EMF, Potential Difference, Current, Power Energy are following:

### EMF (Electromotive force) :

Question: what is Electromotive force ?

Electromotive force (emf) is the force that causes an electric current to flow in an electric circuit.

The S.l. Unit of Electromotive force EMF is volt (V)

### Potential difference :

Question: what is potential difference ?

Potential difference between two points in an electric circuit is that difference in their electrical state which ends to cause flow of electric current between them.

The S.I. unit of potential difference is volt (V)

potential difference equation or potential difference formula :

### Electric Current :

Questions : what are electric current ? or what are electric current ? or electric current define ? or electric current definition ?

The electric current is defined as the rate of flow of electric charge or electrons.

Its S.I. electric current unit is Ampere (A)

#### (a) One Ampere :

The unit of current is ampere. One ampere of current is said to flow in a wire if through any cross section 628 x 106 electrons pass in one second.

As 1 coulomb = 628 x 106  electron charge.

ampere into watt or ampere to watt :

Watts = Amps x Volts

10 Amps x 120 Volts = 1200 Watts.

#### (b) Current :

An electric current is a stream of charged particles, such as electrons or ions, moving through an electrical conductor or space. It is measured as the net rate of flow of electric charge past a region.

i.e. the rate of flow of electron charge flowing per second.

### Electric Power :

The rate at which work is done in an electric circuit is known as electric power =

above mentioned electric power formula .

.The basic unit of electric power is watt.

One Watt : The power in electric circuit is one watt if a electric potential of I volt causes 1 ampere electric current to flow through the circuit.

Derivation of Electric power :

Electric power = (Energy consumed)/Time

P = Heat/time

P = (I²Rt)/t

P = I²R -(1)

Or,

P = (R.I)×I

By ohm’s law, V = R.I

P = V.I

Again, V = RI

V/R = I

Hence, P = V×(V/R)

P = V²/R

SI unit of electrical power is

Joule/second Or watt (W)

Other bigger unit of electric power and their relation with watt

1 kilowatt = 1000 watt

1 megawatt = 10^6 watt

1 gigawatt = 10^9 watt

1 horsepower = 746 watt

### Electrical Energy :

The total amount of work donein an electric circuit is called electrical energy.

Electrical Energy = Voltage x Current x time

The unit of electrical energy is joules or watt-second.

One joule : One joule or watt-second of energy is expended if one ampere current passes through 1 ohm resistance for 1 second.

The joule or watt-second is very small unit. For commercial purposes higher unit is watt-hour or kilowatt-hours are used.

1 watt hour = 1 watt x 1 hour = 1 watt x 3600 sec.

= 3600 watt/sec.

1 kilowatt-hour = 1 kW x 1 hr. =  1000 watt-hr.

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