Electricity Booklet Flashcards
What is the definition of electric current?
The rate of flor of charge
What is the equation that links charge current and time
Charge=current x time
Q=I x t
What is the equation that links potential difference, current and resistance?
Potential difference= current x resistance
V=I x R
What’s the difference between a series and parallel circuit?
A series circuit has only one path for the current to flow; a parallel circuit has more than one
What does ohms law say?
The current though an ohmic conductor (at a constant temperature) is directly proportional to the potential difference across the resistor
What happens to the resistance of a filament lamp as the temperature increases?
As the temperature increases the resistance of a filament lamp also increases
What happens to the resistance of a thermistor as it increases in temperature?
The resistance decreases as the temperature increases
What happens to the resistor of a LDR as the light intensity increases?
The resistance decreases as the light intensity decreases
In what diode can the current flow through a diode?
A current can only flow one way though a diode
Name an application of an LDR/thermistor:
In sensing circuits ( lights turning on when dark/ heat turning on when cold)
How does resistance add in series?
RTOT=R1+R2
What happens to current in series/parallel circuits?
Current is the same everywhere in a series circuit. Current splits in a parallel circuit
What happens to the potential difference in series/parallel circuits?
Potential difference is the same on different paths of a parallel circuit; it splits across components in a series circuit
What happens to the total resistance of two resistors in parallel?
The total resistance of two resistors in parallel is less than the resistance of the smaller resistor
What do we use to measure potential difference/current?
We use a voltmeter in parallel across a component and an ammeter in series.
What is the frequency and potential difference of the mains electricity supply?
50Hz and 230V
What is the difference between AC and DC
AC changes direction, DC remains in the same direction
What are the colours of the live, neutral and earth wires?
Live-brown, neutral-blue, earth-green and yellow stripes
What do the live, neutral and earth wires do?
Live wires carry the AC, neutral wires complete the circuits, earth wires is safety wire.
What happens to the fuse if the current is too high?
The fuse melts making the circuit incomplete, stopping the current from flowing.
Give two equations for electrical power:
P=I x V
P=I^2 x R
Give two equations for energy transfer:
E=P x t
E=Q x V
What is the national grid?
A network of cables and transformers linking power stations and consumers together
What does a step-up transformer do?
It increases the potential difference but decreases the current to reduce heat loss in cables
What does a step-down transformer do?
It decreases the potential difference to a safe level for consumers
What is potential difference?
The difference on the amount of energy that charge carriers have between two points in a circuit. E=Q x V
What is the definition of power?
A measure of how quickly energy is transferred from one form to another. P=E/t
