4A.3 Flashcards
electrons movement throught a ciruit is caused by
an electric force or emf
the electrical force is directly proportional to
the voltage which is proportional to the current
what is resistance
the opposition of flow in an electrical current
how can you calculate the resistance
resistance = potenial diffrence/ current
what does a ohms law states
a current passing through a component is directly proportional to the voltage applied across it, provided that the temperature stays the same
how to draw an I V filament bulb graph
look in page 157
why does the line in the I V filament bulb graph curve
because at higher voltage a higher current passes through, causing an increase in temperature in the metal to increase its resistance as the ions are moving faster now
how do you draw a diode graph
look page 157
what can we tell from a diode I V graph
- diode only conducts in the forward direction (so the current is zero for negative voltages)
- it requires a minimum voltage called the threshold in order for it to start conducting
in diode, the value of the threshold is usually around
0.6
how do you draw a thermistor I V graph
page 157
how does the I V thermistor graph look like that and why
as the voltage increase, the gradient of the curve increase and that is because more voltage means more currents which result in more temperature lowering the resistance since the thermistor is made from semiconducting materials whose atoms release more conduction electrons as the temperature increase
