Measurement of Voltage,Current and Resistance(Ohm's Law)
Electric charge and the coulomb
An electric current consists of aflow of electrons.These electrons are negatively charged and are an important part of an atom.The coulomb is used to measure electric charge.The video clip below gives an illustration of this:-
You may have already used a filament lamp rated at 6V,0.06A(60mA).
The ampere is used to indicate the strength of a current,and is measured in units of coolomb per second.In other words,electric current is the rate at which electric charge in coulomb moves through acircuit.It is easy to remember that one ampere is electric charge flowing at the rate of one coulomb per second,or 1A =1 coulomb/second = 1 C/s.
The 6V ,60mA filament lamp will give 1A is 1 coulomb per second,60 mA=0.06 colomb per second.
.The video clip below gives an illustration of this:-
The letter I is the symbol used for electric current
What the volt measures?The electromotive force of battery is the electrical force between its terminal which makes current flow round a circuit connected to it.The volt is the unit for measuring e.m.f.; for example we say the emf of a battery is 9 volts.
The potential(p.d.) is the difference of electrical force,measured in volts,between the terminals of a component which makes the current flow throughthe component.The volt is the unit of e.m.f. and p.d.and it is measured using a voltmeter which is connected in parallel with the component through which the current flows.
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