P2.3 Currents in electrical circuits Flashcards
What does the current in an ELECTRIC CIRCUIT depend on?
- The resistance of the components
- and the supply
What happens when certain insulating materials are rubbed against each other?
They become electrically charged
Describe, in terms of sub-atomic particles, static electricity
Negatively charged electrons are rubbed off one material and onto the other
What happens when two electrically charged objects are brought together?
They exert a force on each other
Opposites…
…attract
What is electric current?
A flow of electric charge
What is the size of the electric current equal to?
The rate of flow of electric charge
What is charge measured in?
Coulombs, C
What does the p.d. between two objects in an electric circuit equal?
- The work done
- per coulomb of charge
- that passes between the two points
What are current–potential difference graphs used to show?
How the CURRENT through a component VARIES with the P.D. across it.
Describe what you would see on a current-p.d. graph for a resistor at a constant temperature.
Positive line /
What is resistance measured in?
Ω Ohms
The current through a resistor (at a constant temp) is directly proportional to what?
P.d. across the resistor
The current through a COMPONENT depends on what?
Its resistance.
The greater the resistance…
…the smaller the current for a given p.d. across the component
How do you find the p.d. provided by cells connected in series?
Sum of the p.d. of each cell
In a SERIES circuit, describe: (a) How to find the total resistance (b) How the current is shared (c) How the p.d. is shared
(a) SUM of resistance of each component
(b) SAME current
(c) Total p.d. of the supply is SHARED between the components
In a PARALLEL circuit, describe: (a) How to find the total current (b) How the p.d. is shared
(a) Sum of currents through the separate components BECAUSE CURRENT IS SHARED
(b) P.d. is same
As the temperature of the filament increases, what happens to the resistance?
Resistance increases
Is the current through a diode a.c. or d.c.? Why?
DIRECT
The diode has a very high resistance in the reverse direction
When does an LED emit light?
When a current flows through it in a forward direction
As temperature increases, what happens to the resistance of a thermistor?
As light increases, what happens to the resistance of an LDR?
They both decrease
