electrical charge and currenr Flashcards
what is current
flow of electrical charge (flow of electrons)
what is a resistor
slows down flow of electrons / charge
what is a diode
allows current to flow in one direction only protect the components of the battery is the wrong way round
what is an LED
Special type of diode that glows when electricity passes through it
what is a thermistor
thermistors are used as temp sensors, their resistance decreases as the temperature increases. at low temp the resistance of a thermistor is high and little currently can flow through them
at high temp the resistance of a resistor is low and more current can flow through them
what’s a LDR
detects light levels. their resistance decreases as light intensity increases. in the dark and at low light levels resistance of an LDR is high and little current can flow through it. in bright light , resistance of an LDR is low, and more current can flow through
what do u use to measure current
ammeter
equation for total charge
Q=IT
I= current (amps ) T= time (seconds ) Q= charge (coulombs)
what is potential difference
a cell supplies energy to a charge to move it through the circuit and produce a potential a potential energy difference at one end of the circuit compared to the other , this creates a PD
what conclusion can u make abt current in a series circuit
current is the same
what conclusion can u make abt potential difference in a series circuit
potential difference is shared
what conclusion can u make abt current in a parallel circuit
current is shared
what conclusion can u make abt potential difference in a parallel circuit
potential difference is the same
what does current through a component depend on
- resistance of component
- potential difference across component
equation for potential difference
V=IR
V= potednail diff (voltage) I= current (A) R= resistance
how does increasing the length or wire change the current
increasing length of wire decreases the current as it takes longer for the electrons to flow but the potential difference increases so the resistance is higher
as length of wire increases the resistance increases. resistance is directly proportional to length of wire
what does resistance slow down
flow of electrons
what happens in a series circuit when u increase the amount of resistors
the total resistance increases so the electrons flow slower
what happens in a parallel circuit when u increase amount of resistors
the total resistance decreases so the flow of electrons is faster because voltage is same but current increases
why does total resistance decrease in parallel circuit
both resistors have the same potential difference but adding a extra loop, the current has more than one direction to go in. this increases the total current. an increase in current means a decrease in total resistance
what isn’t an ohmic conductor
bulb and diode
what is an ohmic conductor
resistor
what is OHM’s law
the potential difference (voltage) across an ideal conductor is directly proportional to the current through it when the temperature is constant
components that follow this law are called ohmic conductor
what happens to atoms in filament bunk when temp increases
atoms in metal filament vibrate more as the temperature increases. they resists the passage of the electrons through the filament more. the resistance increases as its temp increases
what is direct current
flow of charge is in one direction
what is alternating current
flow of electrons alternates
3 things abt AC
current is consistently changing
voltage alternate
UK mains supply (230V 50hZ)
3 things abt DC
Current is flowing in same direction
voltage is the same
batteries supply this
in the plug which wire is where
N- neutral wire (blue) bottom left
E- earth wire (green &yellow) middle
L- live wire (brown ) right
how can we remember order of wires
Never Eat Lemons
Neutral Earth Live
what does the neutral wire do
completes circuit and carries current away (0V)
what does earth wire do
protect the wiring and safety ( carries currently if there is a fault ) 0V
what does live wire do
provide the alternating potential difference (230V)
what does the fuse do
allows currently of certain valves to pass through. thin piece of metal wire melt to prevent large current to pass through component
what is the national grid
the electrical power is transferred from power station through the step- up transformer which increases the potential difference from 25,000 V to 132,000 V which reduces the energy dissipated to the surroundings. at the step- down transformer it decreases the current and increases the voltage which makes it safer for the home with mains electricity at 230 V
what does a battery with a bigger potential difference supply
a battery with a bigger potential difference will supply more energy to circuit for every coulomb of charge which flows around it
equation for energy transferred
E=QV
E= emery transferred ( J) Q= charge flow (coulomb ) V= potential difference (V)
when is energy transferred electrically
energy is transferred electrically from the mains ac supply to the thermal energy store of the heating element inside the hairdryer
how is energy transferred by heating
energy is transferred by heating from the thermal energy store of the heating element to the thermal energy store of the room
talk about power eating
the lower the power rating the less electricity an appliance uses at a given time
but the higher the power doesn’t mean it transfers more energy usefully
