Electric circuits Flashcards
What is a series circuit
A circuit which consists of two or more components connected end to end Current is the same at all points When several cells are connected in series, their combined EMF = the sum of their individual EMFs
What is a parallel circuit
A circuit which consists of two or more components attached along separate branches of the circuit In a parallel circuit, the current splits up; meaning the current in each branch is smaller than the power supply
Advantages of parallel circuits
The components can be individually controlled, using their own switches If one component stops working the others will continue to function
What is the resistance in series, when two or more resistor are connected
The sum of their individual resistances
Resistors in parallel
When in parallel, resistance decreases and is less than the resistance of any individual component. e.g. If two resistors have the same resistance, it halfs
Equation for resistance in parallel circuit
1/R = 1/R1 + 1/R2
What does a relay switch consist of
A coil (electromagnet)
A magnetic switch
How does a relay work?
When there is a current in a coil, it attracts the switch do to the created magnetic field which closes it and completes the circuit
This can be used to control a switch in a separate circuit as shwon in the above diagram
What is a thermistor
A thermistor is a resistor which changes its resistancew when it is heated
Hotter - resistance decreases
Colder - resistance increases
What is an LDR
A type of resistor which changes its reistance when light on shone on it
More light - decreased resistance
Less light - increased resistance
What is a sensing circuit
When thermistors and LDRs are used to create heat or light sensitive circuits
What is a diode
A component which only allows a current when the potential differene is in the direction of the arrow
A diode is a component which only allows charge to flow in one direction
e.g. if an a.c. cicuit is connected to a diode it will only have current half the time
