Currents Flashcards
What happens when certain insulating materials are rubbed together?
they become electrically charged
negatively charged electrons are rubbed off one material onto the other
the material that gains electrons become negatively charged, vice versa
(static electricity)
What happens when two electrically charged objects are brought together?
they exert a force on each other
two objects that carry the same charge repel, vice versa
What is an electrical current?
the flow of electric charge
the size of the current is the rate of flow of electric charge
the size is given by the equation:
I is the current in amps, A
Q is the charge in coulombs, C
t is the time in seconds, s
What is potential difference?
And how is energy transferred measured using potential difference?
it is voltage
the voltage between two points in an electrical circuit is the work done per coulomb of charge that passes between the points
The symbols you should know
not a flashcard, don’t expect an answer
http://static.aqa.org.uk/assets/image/0003/47505/Electrical-circuit-symbols.jpg
What are current-potential difference graphs used to show?
show how the current through a component varies with the potential difference across it
How can the resistance of component be found?
measuring the current through and the potential difference across the component
What does the current through a component depend on?
its resistance
the greater the resistance, the smaller the current for a given potential difference across the compound
What provides the potential difference across a component?
the cells
the cells connected in series is the sum of the potential difference of each cell
depending on the direction in which they are connected
For components connected in series:
the total resistance is the sum of resistance in each component
there is the same current through each component
the total potential difference of the supply is shared between the components
For components connected in parallel:
the potential difference across each component is the same
the total current through the whole circuit is the sum of the current through the separate components
What happens to the resistance of a filament bulb as temperature increases
it increases
s shaped current-potential difference graph
Explain resistance in terms of ions and electrons
An electric current flows when electrons move through a conductor, such as a metal wire
The moving electrons can collide with the ions in the metal. This makes it more difficult for the current to flow, and causes resistance
The resistance of a long wire is greater than the resistance of a short wire because electrons collide with ions more often
The resistance of a thin wire is greater than the resistance of a thick wire because a thin wire has fewer electrons to carry the current
Describe the current and resistance of a diode?
current only flows in one direction
high resistance in the reverse direction
L (rotated 90 degrees anticlockwise) shapes current-potential difference graph
Why are LED used and how do they work?
LED emits light when a current flows through it in a forward direction
they use a much smaller current and are more efficient
