electrity Flashcards
how does a fuse protect a circuit?
melts it causing it to be broken
effects of voltage increase on temp
causes greater rate of electron collisions causing increase in temp
series circuit features
voltage is shared
all elements are connected in a single loop
parallel circuit features
switch on/off indecently
if one elements breaks the others still work
more power is available
LED
light emitting diode
thermistor
semiconductor that changes resistance with temperature
Diode
it lets current flow in one direction
why does the lamp shine
wire gets hot and gives out light
metal filament lamp graph
light bulb heats up
current increases so resistance increases
so there is a lower voltage causing the graph to curve
if electrical plug becomes warm?
input power increases
input current increases
positively charged or negatively charged which can move
only negatively charged particles can move
they will move from an area of negative charge to an earthed area
why is there a spark
there is a potential difference
when the optional difference is high enough electrons jump across
how to tell the charge?
bring them close to one another - like charges repel
current defo
flow of charge
voltage defo
energy transferred per unit charge passed
Direct Current
Electric current in a circuit that is in one direction only.
Alternating Current
Electric current in a circuit that repeatedly reverses its direction.
What does the earth wire protect?
The user
Circuit Breaker
An electromagnetic switch that opens and cuts the current off off if too much current passes through it.
Why are circuit breakers better than fuses?
They work faster
They can be reset
Rubbing a polythene rod with a dry cloth.
Transfers electrons to the surface atoms of rod from the cloth, so the rod becomes negatively charged.
Rubbing a perspex rod with a dry cloth..
Transfers electrons from the surface atoms of the rod to the cloth, so the rod becomes positively charged.(loses electrons)
Battery.
A cell is necessary to push electrons around a complete circuit. A battery consists of two or more cells.
Ammeter.
Used to measure current.
Resistor.
Limits the current in a circuit.
Variable Resistor.
allows the current to be varied.
Explain why only electrons are transferred when objects are charged by friction.
Electrons are located in the outer shells of an atom and are easily removed.
However, protons are located in the nucleus at the centre of the atom and are tightly bound.
Explain how a gold leaf electroscope works.
When it is charged, both the rod and leaf adopt the same charge and the gold leaf is repelled from the rod and rises.
The greater the charge, the greater the repulsion the further the gold foil rises.
There is a large insulated coil of wire inside the kettle. Explain why this coil of wire gets hot when the kettle is switched on.
MP1. there is a current in
the coil / wire;
MP2. coil / wire has resistance;
MP3. electrical energy transferred to thermal energy;
