Electricity Flashcards
If you increase the resistance of the variable resistor what will happen to the potential difference of the fixed resistor?
It will decrease
Behaviour of a thermistor
Temp up Resistance Down
Describe the behaviour of an LDR
The resistance of an LDR decreases with increasing light intensity
What is meant by a superconductor?
A wire or device made of a material with zero resistivity at and below a critical temperature
In semiconductors, what effect does increasing the number of charge carriers have on the resistance?
Number of charge carriers increases and the resistance decreases
Why shouldn’t you connect non identical cells in parallel?
Because the one with greater emf will force a current back through the other
What is the resistance of an ideal voltmeter?
Infinite
In a circuit with a battery, which direction do the electrons travel through wires?
negative to positive terminal
On a graph of resistance and length, how can resistivity be found?
The gradient multiplied by cross sectional area
Define electromotive force
The electrical energy produced per unit charge passing through the source
What is the resistance of an ideal ammeter?
Zero
What is Kirchoffs first law?
At any junction, total current in = total current out
What is Kirchoffs second law?
For any complete loop, the sum of emfs around the loop is equal to the sum of potential drops around the loop.
What is Ohms law?
The p.d across a metallic conductor is proportional to current through it provided physical conditions don’t change
What is the effect of adding 2 or more cells in series in different directions?
Net emf is the difference between the emfs in each direction
