Paper 2-SP10,SP11 Flashcards
What metal is used for electrical wiring?
Copper.
What do metal wires need?
Free electrons.
What happens when a battery is attacked to the wire?
The voltage ‘pushes’ the free electrons around the circuit. The electrons are negative so they move towards the positive terminal of the battery.
What is the conventional current?
Positive to negative.
Show the difference between the conventional direction of current flow and the direction of electron flow?
What is the symbol and component for a switch(open)?
What is the symbol and component for a cell?
What are the symbol and component for a battery?
What are the symbol and component for a lamp?
What are the symbol and component for an ammeter?
What is the symbol and component for a voltmeter?
What are the two types of circuits?
Series and parallel.
What is a series circuit?
There is just one route the current can take around the circuit.
What is a parallel circuit?
There are are junctions that allow the current to take different routes.
How do lamps work in series circuits as compared to parallel?
Lamps cannot be switched on and off individually, and if one lamp fails, they will all switch off whereas in parallel circuits they can be switched separately.
What is electrical current measured in?
Amperes(Amps)(A).
What is electrical current measured with?
An ammeter.
Is current conserved?
Yes and the current leaving the positive terminal of the battery is the same as the current arriving at the negative terminal. Total current entering junction same as leaving.
What do you need to push current around an electrical circuit?
A potential difference.
What is potential difference also called?
Voltage.
What also must happen for a current to flow?
The circuit must be closed and contain a source of potential difference such as a cell or battery. The elctrons will then all move together.
What is the potential difference like across each of the branches in a parallel circuit?
It is always the same, when there is more than one component in a branch of a circuit, the potential differences across all components add up.
What is potential difference measured in?
Volts.
What is potential difference measured with?
A voltmeter,
Where does the electric current flow from?
Negative to positive.
Is energy conserved in a current?
No.
What is conventional current?
Pos to neg and we draw it like that as scientists used to be dumb.
What happens to energy in electrical circuits?
It is transferred.
What happens to the voltage in series circuits?
It is split.
What happens to potential differences on parallel circuits?
For components connected in parallel, the potential differences is the same.
Look at this.
What do all the cells in a battery have to be?
Pointing in the same direction or the PT will be 0, well if there is more it just cancels out so like yh watch “potential difference from batteries” by free science lessons.
What is the equation for charge flow?
Current x time
What is charge flow measured in?
C(coulombs)
What is the equation for energy transferred?
Charge flow x potential difference.
What is resistance measured in?
Ohms (omega symbol)
What is the equation for potential difference?
Current x resistance
What do resistors do in series?
Total resistance is increased because pathway becomes harder, PD is shared between resistors but may not be equal. Greater PD across resistors with higher resistances.
What do resistors do in parallel circuits?
Total resistance is less the resistance of individual resistors because there are more paths for the current.
Show the graph of current with different things.
What happens to filament lamps as the potential difference increases?
Hotter and brighter but the resistance increases so they are not in proportion.
How does the resistance of diodes change?
Low resistance if PD is in one direction but high PD is in the opposite direction so current can only flow in one direction.
What is an LDR?
Light-dependant resistor has a high resistance in the dark but the resistance gets smaller when the light intensity increases.
What is the resistance of thermistors like?
High resistance at low temperatures but as the temperature increases the resistance decreases.
What is resistance?
The PD required to drive a current through a component.
Why is resistance not bad?
Sometimes we want to add it through a resistor.
What is the symbol for a resistor?
Hollow rectangle.
What is the current through a resistor?
Directly proportional to the potential difference. Resistors like these are called These are called ohmic conductors but this only applies if the temp does not change.
What is the graph for current and PD like for an ohmic conductor?
Constant.
What does the word filament mean?
A very fine wire.
What is the graph for a filament lamp like for PD and current?
Not directly proportional as the filament gets hot so the resistance increases.