2.2.1-2.2.5 - Components in series and parallel Flashcards
What is current like in a series circut?
In a circuit that is a closed-loop, such as a series circuit, the current is the same value at any point
This is because the number of electrons per second that passes through one part of the circuit is the same number that passes through any other part
This means that all components in a closed-loop have the same current
What does the current in a circut depend on?
The amount of current flowing around a series circuit depends on two things:
The voltage of the power source
The number (and type) of components in the circuit
How can the current in a circut be Changed?
Increasing the voltage of the power source drives more current around the circuit
So, decreasing the voltage of the power source reduces the current
Increasing the number of components in the circuit increases the total resistance
Hence less current flows through the circuit
What is a parallel circut?
A junction in a parallel circuit is where two or more wires meet
The current is always split at a circuit junction
What is the current like a parallel circut
The current is conserved
This means the amount of current flowing into the junction is equal to the amount of current flowing out of it
This is because charge is conserved
Note that the current does not always split equally – often there will be more current in some branches than in others
The current in each branch will only be identical if the resistance of the components along each branch is identical
Why does current behave in this way?
Current behaves in this way because it is the flow of electrons:
Electrons are physical matter – they cannot be created or destroyed
This means the total number of electrons (and hence current) going around a circuit must remain the same
When the electrons reach a junction, however, some of them will go one way and the rest will go the other
What is the current like in a series compared to a parallel?
Series:
The current is the same at all points ie. through each component
The total potential difference of the power supply is shared between the components
Parallel:
The total current through the whole circuit is the sum of the currents through the separate components
The potential difference across each component is the same
What are the advantages ad disadvantage of a series circut?
A series circuit consists of a string of two or more components connected in a loop
The advantages of a series circuit are:
All of the components can be controlled by a single switch
Fewer wires are required
The disadvantages of a series circuit are:
The components cannot be controlled separately
If one component breaks, they will all stop working as well
What are the advantages and disadvantages of a parallel circut?
A parallel circuit consists of two or more components attached across different branches of the circuit
The advantages of a parallel circuit are:
The components can be individually controlled, using their own switches
If one component breaks, then the others will continue to function
The disadvantages of a parallel circuit are:
Many more wires involved so much more complicated to set up
All components have the same voltage as the supply, so harder to control if components need to have different voltages
What does a series circut look like?
What does a parallel circut look like?
What are resistors in a series circut
When two or more resistors are connected in series, the total (or combined) resistance is equal to the sum of their individual resistances
Where R is the total resistance, in Ohms (Ω)
Increasing the number of resistors increases the overall resistance, as the charge now has more resistors to pass through
The total voltage is also the sum of the voltages across each of the individual resistors
In a series circuit, the voltage of the power supply is shared between all components
What are IV graphs?
As the potential difference across a component is increased, the current also increases
This is because potential difference and current are proportional
The precise relationship between voltage and current is different for different components and can be shown on an IV graph, including in:
Fixed resistors & wires
Filament lamps
Diodes
What are fixed resistors and wire graphs and what are their features?
The current through a fixed resistor or a wire increases as the potential difference (or voltage) across it increases
In other words, current is directly proportional to the potential difference for a fixed resistor (or a wire)
This relationship is true because the resistance of the fixed resistor (or wire) stays constant
An IV graph shows that the line is straight and goes through the origin, as shown in the image below:
What does a fixed resistor and wire graph look like?
What does a filament graph look like?
What does a diode graph look like?
Show the apparatus for this experiment ?
What do the resistor and variable resistor look like?
What are thermistors ?
A thermistor is a temperature-dependent resistor
It is represented by the following circuit
The resistance of a thermistor changes depending on its temperature
As the temperature increases the resistance of a thermistor decreases and vice versa
What are LDRS?
The resistance of an LDR changes depending on the light intensity on it
As the light intensity increases the resistance of an LDR decreases and vice versa
What are lamps and LEDS?
Lamps illuminate (light up) when a current flows in a circuit
LEDs are types of diodes
This means they only allow current to pass in one direction through them and will only light if the current passes in that direction
LEDs also illuminate when a current flows in a circuit (provided the LED is placed in the correct direction)
Since both electrical components have a visual response to current, they can be used to indicate the presence of a current in a circuit
