CHARGE, CURRENT AND POTENTIAL DIFFERENCE Flashcards
Define current
Current is the rate of flow of charge
What is the equation to find current?
I=Q/T
Define one coulomb
One coulomb is the amount of charge that passes a point in 1 second when the current is 1 ampere
How would you measure current?
By using an ammeter
State the elementary charge
1.6 x 10^-19
What will the net charge always be on any object in terms of e.
a multiple of e and therefore charge is quantised
What is potential difference?
It is the Work done per unit charge
State the equation to calculate P.D.
V=W/Q
Define one volt
One volt is when you do one joule of work moving one column of charge through the component.
How can you measure P.D.?
Using a voltmeter
What happens to the P.D. in a parallel circuit?
It is all the same
State the equation to find kinetic energy?
eV=0.5mv^2
Define Mean drift velocity
It is the average velocity of charge carriers
What is roughly a charge carriers speed?
10^6
What equation would you use if you were to find mean drift velocity?
I=nAve
Complete the statement- if you double the number of electrons…..
the current doubles
Complete the statement- if you double the area…..
the current doubles
Complete the statement- if the electrons move twice as fast…
the current doubles
In metals what happens to n (the number density of electrons)?
It is big n and drift velocity is small
In semiconductors what happens to n (the number density of electrons)?
fewer charge carriers so drift velocity needs to be higher
In a perfect insulator what happens to n (the number density of electrons)?
Have a very very small n and you would get no current
Name a liquid that is an insulator
Sodium chloride
What happens to sodium chloride once molten?
The liquid conducts
What is an electrolyte?
A substance containing ions that conducts electricity
How do you form a spark?
Gases are insulators, but if you apply a high enough voltage, electrons get ripped out of atoms giving you ions along a path.
