Electricity Flashcards
what does it mean is the charge is fast
there is a large electrical current
what carries the charge in metals and what is produced
the electrons which produce an electric current
what is current like in a series circuit
the same at all point
what is voltage like in a series circuit
it is shared between the components
advantages and disadvantages of series circuits
advantages - requires fewer wires
disadvantages - if a fault occurs the whole circuit stops working
what is current like in a parallel circuit
the loop adds up to the total current from the supply
what is voltage like in parallel circuits
the same across each loop
advantages and disadvantages of parallel circuits
advantages - each loop can be controlled seperatley and if one stops working the rest still work
disadvantages - they are more complicated to construct
how do you calculate the total resistance when the resistors are connected
adding the value of the individual resistors
what is current
the rate of flow of charge at a point in the circuit
how is current measured and where is it connected
with an ammeter in series
what is voltage
the amount of energy transferred between two points in a circuit
what is resistance
the opposition to the flow of current
what happens to the resistance of the LDR as the light gets brighter
the resistance decreases
what happens to the resistance of the thermistor as the temperature increases
the resistance decreases
does a thermistor’s and LDR’sresistance follow a linear pattern?
no becuase as the temperature increases the rate of decrease of resistance falls
what sizes do fuses come in
3A, 5A and 13A
what should you do when picking a fuse and why
the smallest one which won’t melt
This makes sure that more current doesn’t keep flowing through the circuit and causing more damage to the equipment, or, causing a fire
what is circuit breaker
an electromagnetic switch which is a safety device
what does a circuit breaker do
breaks the circuit if the current rises over a certain value
what do many appliences have as a insultor
plastic casings
what does double insulation mean and why does it help with safety
all parts of the appliance are insulated in plastic
if a human were to touch the live wire then they could become electrocuted
how can electrical energy be supplied
by plugging into a main (power supply, battery or cell)
what does d.c current stand for
direct current
what does a.c current stand for
alternating current
what is d.c current
a d.c supply produces a charge through a circuit in one direction
what is a.c current
an a.c supply produces a flow of charge that regularley reverses its direction
what is static electricity
involves the transfer of electric charges between objects. In electrostatic phenomena, objects become charged through electron transfer by friction, contact, or induction
what charges are ALWAYS fixed in static electricity
the positive charges
what is an example of static electricity
balloon sticking to the wall
what are uses of electrostatic chrages
paint sprayer
inkjet printers
photocopiers
electrostatic filters
what are examples of dangers of electrostatic charge
lightning
fueling aircraft
what can LED’s be used for
to indicate the presence of current in a circuit
how does current flow
from the positive terminal to the negative terminal of a cell
why are metals used as wires
because metal is a good conductor of electrical current
why is current conserved at a junction
becuase charge is always conserved
what is a fuse
a thin peice of whire which overheats and melts if the current is too high which pretects the circuit
what do earth wires do
provide a safe route for current to flow through in case of a short circuit
why is double insulation good
it compleately covers the appliances electrical components so the earth wire cannot touch the metal casing
what does it mean to charge a body
adding, removing of electrons creating ions
what do metals do
conduct and allow electrons to flow through them
what do insulators do
slow down the flow of electrons
explain an experiment for static electricity between 2 insulators
when 2 insulators are rubbed together the friction causes electrons to move from one to the other and they become charged
for example a rod with a cloth
what are the 3 wires in a plug
live, neutral and earth
how does a current in a resistor result in the electrical transfer of energy and an increase in temperature
Resistance causes transfer of electrical energy to heat energy
domestic examples of when a resistor gets hot when a electric current passes through
toasters - contain coils of wire with really high resistance
when the current passes through the coil the temperature increases and give off infered radiation
Electric kettles- the heating element is placed at the bottom of the kettle
The heat is then absorbed by water and distributed throughout the whole liquid by convection
what are examples of mains which produce d.c current
cells and batteries
what are examples of mains which produce a.c current
Produced by electrical generators i.e. mains electricity
what terminals do ac and dc current have
a.c has 2 identical terminals
d.c has positive and negative terminals
why is parallel more appropiate for domestic lighting
each light switch in you house is part of a branch of a parallel circuit. it just turns one light (or one set of lights) on and off
what does the current in series depend on
the applied voltage
the number and nature of other components (eg bulbs)
current - voltage graphs: what line does a metal fillament lamp have
curve
current - voltage graphs: what line does a wire have
straight through zero
current - voltage graphs: what line do different resistors have
striaght lines through zero
current - voltage graphs: what line does a diode have
striaght to curve
why do metal filament lamps have a curve graph
as the temperature of the metal filament increases the resistance increases
why does a wire have a straight line through 0
the current through a wire is proportional to voltage (at constant temperature)
why do different resistors have a straight line through zero
the current through a resistor is proportional to voltage
why do diodes have a straight - curve line
current will only flow in one direction
apparatus for investigating current voltage graphs
an ammeter - to measure the current through the component
a voltmeter - to measure the voltage across the component
a variable resistor - to vary the current through the circuit
a power source - to provide a source of potential difference (voltage)
wires - to connect the components together in a circuit
what is the qualitative effect of changing resistance on the current in a circuit
as you increase the resistance in a circuit, the current will decrease.
describe the qualitative variation of resistance of thermistors with temperature
At low temperatures, the resistance of a thermistor is high, and little current can flow through them.
At high temperatures, the resistance of a thermistor is low, and more current can flow through them.
what is current
in a sloid mettalic conductor
the flow of negitivley charged electrons
examples of conductors
metals - copper and silver
how are positive and negative electrostatic charges produced on materials by the loss and gain of electrons
The material that gains electrons becomes negatively charged. The material that loses electrons is left with a positive charge
what are the forces of attraction and repulsion
attraction between unlike charges
repulsion between like charges
