P2 Parallel Circuits (page 184) Flashcards
Explain what Parallel Circuits are?
each component is separately connected to the +ve of the supply (accept ammeters, which are always connected in series).
What affect will a parallel circuit have if you remove or disconnect one of them?
it will hardly affect the others at all if you remove or disconnect one.
Most things are connected by parallel circuits, give some examples?
e.g. in cars and in household electrics. You have to be able to switch everything on and off separately.
Everyday circuits often include a mixture of what parts?
a mixture of series and parallel parts.
Parallel Circuits - means Independence and Isolation.
See diagram 1 on page 184.
What is meant by Potential Difference’?
it is the same across all components.
In parallel circuits all components get the full source pd, so the potential difference is the same across all components:
V1 = V2 = …
What is meant in parallel circuits all components get the full source of pd?
this means that idential bulbs connected in parallel will all be at the same brightness.
In parallel circuits the total current flowing around the circuit is equal to what?
equal to the total of all the currents through the separate components
I total = I1 + I2 + …
In a parallel circuit, there are junctions where the current does what?
where the current either splits or rejoins.
The total current going into a junction has to equal the total current leaving.
(see picture on page 184 showing the currant is shared between branches).
If two identical components are connected in parallel, will the same current flow run through each component?
Yes.
If you have two resistors in parallel, what will happen?
their total resistance is less than the resistance of the smallest of the two resistors.
Explain what is meant by ‘in parallel’ if you have two resistors?
both resistors have the same potential difference across them as the source.
This means the ‘pushing force’ making the current flow is the same as the source pd for each resistor that you add.
But by adding another loop, the current has more than one direction to go in.
This increases the total current that can flow around the circuit. Using V - IR, an increase in current means a decrease in the total resistance of the circuit.
(Adding a resistor in Parallel reduces the total resistance).
A circuit contains three resistors, each connected in parallel with a cell. Explain what happens to the total current and resistance in the circuit when one resistor is removed? (4 marks)
The total current through the circuit decreases (1 mark) as there are fewer paths for the current to take (1 mark). The total resistance of the circuit increases (1 mark). as using V = IR, a decrease in the total current means an increase in the total resistance (1 mark).
Draw a circuit diagram for two filament lamps connected in parallel to a battery. Both of the lamps can be switched on and off without affecting each other (3 marks).
Look at page 247, p.184, Q2 diagram
1 mark for the correct circuit symbols
1 mark for two bulbs connected in parallel
1 mark for both switches being on the same branches as the lamps.
