Currents In Electrical Circults Flashcards
What happend to certain insulated materials when they are rubbed togetehr?
They become electricaly charwged
negitively chaged electrons are rubbed off one material and onto another
What happens to the insulated material which gains electrons?
It becomes negatively changed
What happens to the insualted material which loses electron?
It is left with an equal positive charged
What happens when 2 electrically charged objects are brought together?
They exert a force on each other
Two objects that carry the same type of charge…
Repel
Two objects that carry different charge…
Attract
What are electrical charges allowed to do in certain substances, such as metals?
They can move easily
What is an elecric current?
it is a flow of electric charges
what is the size of the electric current?
It is the rate of flow of electric charges
The equation for the size of the current is:
Q
I = — What do these symbos mean?
t
I = current in Amps
Q =charge in coulombs
t = time in seconds
The equation for the potential differnce is:
W
V= — What do these symbos mean?
Q
V = pottential difference in volts W = work done in joules Q = charge in coulombs
What are current-potential graphs used to show?
They are used to show how current through a component varies with the potential difference across it
Who can the resistance of a component be found?
by measuring the current through, and potential difference across the resistor
The equation for the resitance is:
V
R = — What do these symbos mean?
I
R = the resistace in ohms V = pottential difference in volks I = current in amps
What does the current of a component depend on?
It depends on its resistane. the greater the resistanxe the smaller the currenet for a given potantial difference across the comnponent
The potential difference provided by 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 to a series circuit the total tesistance it the sum of…
The resistance of each component
For components connected to a series circuit, the current is…
the same in each component
For components connected to a series circuit, the total potential difference to the supply is…
shared between the components
For components connected to a parallel circuit, the potential differnce across each component is…
the same
For components connected to a parralel circuit the total current through the whole circuit id the sum of…
The current throuhg the seperate components
The resistance in a filament bulb …… as the temperature …….
increases and increases
decreases and decreases
The current through a diode flows in which direction?
only one
What is the resistant of a diode in the revers direction?
very high
When does resistance increase?
The length of the wire increases
The thickness of the wire decreases
How is resistance caused?
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.
Why does the increase of the length of the wire cause as increase in resistance?
The resistance of a long wire is greater than the resistance of a short wire because electrons collide with ions more often.
Why does a thinner cause a greater resistance?
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.
When does an LED emit light?
when a current flows thorugh it in the forwards direction
Why is there an increase in the use of LEDs for light?
Because they use a much smaller current than other forms of lighting
The resistance of a LDR decreases as light intensity…..
Increases
The resisatance of a thermistor decreases as the temperature…
Increase
