ELECTRICAL QUANTITIES

VOLTAGE OR POTENTIAL DIFFERENCE

 The amount of energy that a generator (electrochemical cell or battery) can transfer to electrons depends on its voltage (V) or electric tension. This is measured in volts (v).

If we want to measure voltage, we can use a voltmeter. This device has two wires (probes) that must be conected in parallel.

MEASURING ELECTRIC CURRENT


Electric current (I)  is the time rate of flow of electric charge, in the direction that a positive moving charge would take and having magnitude equal to the quantity of charge per unit time: measured in amperes.


Electric current is measured in amperes or amps (A) in the InternationalSystem or SI (from the French, Le Systéme International).






1A=1C/1s




We can use an ammeter to measure electric current. This instrument is connected in series, so that all the electrons must pass through it.




ELECTRICAL RESISTANCE : OHM´S LAW


The resistance (R) is the opposition that a substance offers to the flow of electric current. The standard unit of resistance is the ohm, sometimes written out as a word, and sometimes symbolized by the uppercase Greek letter omega:Ω . When an electric current of one ampere passes through a component across which a potential difference (voltage) of one volt exists, then the resistance of that component is one ohm.


OHM´S LAW


R=V/I    -   V=R x I   -   I=V/R


ELECTRICAL ENERGY AND POWER


ELECTRICAL ENERGY


 We can calculate the energy (E) that is consumed: E=V x I x t
In the SI, this electrical energy is measured in joules (J).


ELECTRICAL POWER


The electric power of load is the amount of energy that it can transform over a certain amount of time. Electric power is measured in watts (W) or kilowatts (kW).


If an electric current (I) flows at a particular tensión (V), we can calculate the power (P) that is consumed: 


P=V x I