electrical quantities Flashcards
how to charge a negative rod by friction
rub a rod with cloth- negative electrons will move from the cloth to the rod- cloth becomes positive and
non metals can be charged by what
friction
to protons or electrons move
electrons
neutral objects are attracted or repuled to charged objects
atrracted
positive point field lines
away from point
negative point field lines
towards point
uniform electric field field lines
towards negatuve plate
how to charge by induction
1) uncharged metal sphere on a insulator
2) charged rod close to sphere
3) earth the metal- neelectrons neutralize + charges
4) remove earth connection
what is electric current
the rate of flow of charge
formula of current
current= charge/time
why are metals good conducters of electricity
because theyr have free electrons which are free to move and carry a charge
what is a non metal that conducts
graphite carbon
what are examples of insulators
water
how does temperature effect current
the bigger the temperature the flow of current decreases and resistance increases becuse electrons are harder to move with more metal ions collding
what is potential difference or “voltage”
p.d pushes electrons and gives them energy to move around a circuit
work done by a unit of charge passing by a component
p.d= work/charge
the cells in series adds uo to the total
p.d (e.m.f)
what is resistance
the opposition to the flow of current
resistance=p.d/current
what is conventional current
the flow of electrons
what is electromotive force
the electrical work done by a souce in moving unit charge around a complete cirasuit
emf formula
e=w work/ charge
what do electrical circuit do
they transfer energy from a source of electrical energy like cells or a main supply to the circuit components eg: lamps and then to the surroundings as heat
electrical power supplied by cells= …..
total power udes by circuit components
what is power
power is the rate of doing work (changing energy)
power= energy change/ time
or
power = voltage x current
power= v2/R
what is ohms law
current is porportional to potential difference at constant temperature
what is the difference between ac and dc
In DC, the electrons flow steadily in a single direction, while electrons keep switching directions, going forward and then backwards in AC.
flow of electrons and direction of current
State that conventional current is from positive
to negative and that the flow of free electrons is
from negative to positive
resistance formula
resistance= V/I
relaishonship between length of wire and resistance
the bigger the length the bigger the resistance
porportional
R1/L1= R2/L2
relaishonship between cross section of a waire amd resstance
resistance is inversely porportional to cross section
R1xA1=R2xA2
relaishonship between free electrons and resstance
the more free electrons the mor resistanve
R1xR1^2=R2xR2^2
relaishonship between temperature and resistance
the bigger the temp the bigger the resistance
R1xd1^2/L1=R2xd2^2/L2
