P2.3 Flashcards
What does a current in an electric circuit depend on
The resistance of the components and the supply
Different forms of lighting
Filament bulbs
Fluorescent bulbs
Light emitting diodes
What happens when certain insulating materials are rubbed against each other
They become electrically charged
What is rubbed off one material to the other
Negatively charged electrons
The material that gains electrons becomes
Negatively charged
The material that loses electrons
Is left with an equal positive charge
What happens when two electrically charged objects are brought together
They exert a force a force on each other
Electrical charges can move
Easily through some substances e.g metals
What is an electric current
A flow of electric charge
What is the size of the electric current
The rate of flow of electric charge
What is the potential difference between two points in an electric circuit
The work done per coulomb of charge that passes between the points
What are current potential difference graphs used for
To show how the current through a component varies with the potential difference across it
How can the resistance of a component be found
By measuring the current through and the potential difference across
The current through a resistor is directly proportional to
The potential difference across the resistor
What does current through a component depend on
Its resisistance
The greater the resistance,
The smaller the current for a given potential difference across the component
What is the potential difference provided by cells connected in series
The sum of the potential difference of each cell ( depending on the direction )
For components connected in series
Total resistance-The sum of the resistance of each component
There is the same current through each component
Total potential difference is shared between the components
For components connected in parallel
The potential difference across each component is the same
Total current through the whole circuit is the sum of the currents through the separate components
The resistance of a filament bulb increases
As the temperature of the filament increases
The current through a diode
Flows in direction only
What does the diode have
A very high resistance in the reverse direction
When does an led emit light
When a current flows through it in the forward direction
Why is there an increasing use of LEDs for lighting
They use a much smaller current than other forms of lighting
The resistance of a light dependent resistor decreases
As light intensity increases
The resistance of a thermistor decreases
The temperature increases
Where are crumple zones positioned
Front and back of car
What do crumple zones do
They increase the impact time,decreasing the for e produced by the change in momentum
What are side impact bars
Strong metal tubes fitted into car door panels
How do side impact bars help
They help direct the kinetic energy of the crash away from the passengers to other areas of the car
How do seat belts help in a car crash
They stretch slightly increasing the time taken for the wearer to stop
Reduce forces acting in the chest
Some kinetic energy is absorbed by the seatbelt by stretching
How do airbags help in a car crash
Slow u down more gradually and prevent u from hitting hard surfaces inside the car
The more powerful the engine is
The more energy it transfers from its fuel every second and so faster top speed
What is current
The flow of electric charge round the circuit.
Only will flow through a component if their is potential difference across the component
Potential difference
The driving force that pushes the current round the circuit
What is resistance
Anything in the circuit which slows the flow down
What does total charge through a circuit depend on
Current and time
