Static and Current Electricity Flashcards
(27 cards)
Symbol of charge
Q
Unit of charge
Coulomb(C)
Why does a positive charge occur
Shortage of electrons
Why does a negative charge occur
Excess of electrons
Methods of charging?
Friction, conduction, induction
What is the law of conservation of charge
Electric charge can neither be created nor destroyed
Law of electrostatics
Like charges repel, unlike charges attract
What is Coulomb’s law
The force between two point charges is directly proportional to the product of their charges and inversely proportional to the square of their distance apart
Equation for Coulomb’s law
F=kq1q2/r^2
What is an electric field
Region where an electric charge will experience a force
Rule of field lines
- start perpendicular to the charged surface
- they go from + to -
- they never touch or cross
- the denser they are, the stronger the field is
What is essential for current to flow
- power supply
* complete circuit
What is current
A flow of ‘free electrons’
Formal for current
I=Q/t
Current unit
Amperes
What is voltage or potential difference
The work done(or energy transferred) per unit charge across a component
What is the equation for voltage
V=w/q=e/q
What is emf
Electromotive force is he voltage provided by the power supply on open circuit
• work done per unit charge
•e=w/q
Unit for resistance
Ohm(Omega)
What is resistance
It is a measure of opposition to current flow
What causes resistance in metals
Vibrating metal ions in the lattice hindering the flow of ‘free’ electrons
Resistance formula
R=p(resistivity)l(length)/A(cross sectional area)
What is ohms law
The current flowing in a conductor is directly proportional to the potential difference across its ends provided the temperature and other physical conditions remain constant
Ohms law equation
V=IR
