Electricity Flashcards
power supply symbol
two filled-in dots witha gap between them
voltage/power rating meaning
the maximum p.d./power that a device can operate at safely
threshold voltage meaning
A value of p.d., above which allows current to flow easily in a diode
potential difference meaning
The work done per unit charge.
1V = ?
1 J/C
Ideal voltmeters/ammeters meaning
Ideal voltmetes have infinite resistance so no current flows through them - to measure the p.d. all the current should pass through the resistor and none through the voltmeter
Ideal ammeters have no resistance so have no p.d. across tje,
emf meaning
the terminal potential difference (p.d. across the power supply e.g. cell) when the current is 0
the amount of energy provided for each coulomb of charge passing through (ε = E / Q)
What happens in a wire when a complete circuit is formed with a cell?
when a p.d. is induced, electrons move towards the positive charge
How do you calculate the resistance for a non-ohmic conductor?
Read off the values for current and p.d.
Explain why an IV graph of a filament lamp looks like that.
- As the current increases, its temperature also increases
- This causes the particles in the metal to vibrate more
- This makes it harder for the charge-carrying electrons to travel through
- This increases the bulb’s resistance as the current can’t flow as easily
Why do filament bulbs’ IV graphs plateau?
As the current and so temeprature increases, the resistance increases, which decreases the current.
What does a V-I graph for a filament lamp look like?
look online
quadrant 1 = x2 graph
quadrant 3 = -x2 graph
forward bias meaning
The direction in a diode which allows current to flow
reverse bias meaning
The direction in a diode where the resistance is high so the current is small
resistivity meaning
The property of a material