Paper 1- Electricity Flashcards
Define current
The rate of flow of charge
Define potential difference
The work done per unit charge
State Ohm’s Law
The current through a metallic conductor is proportional to the potential difference across it provided the temperature remains constant
When the temperature of a thermistor increases, its resistance….
Decreases
When the light intensity incident on an LDR increases, its resistance….
Decreases
In a parallel circuit the potential difference across each branch is…
The same
In a parallel circuit the current across each branch is…
Split based on the resistance of each branch (higher resistance = lower current due to V=IR)
What is the potential divider equation?
V=R/R(total) X V(total)
What is a potential divider?
A combination of resistors in series that splits the resistance between components
State Kirchoff’s first law
At any junction, Total current in = total current out
State Kirchoff’s second law
Algebraic sum of EMFs= Algebraic sum of IR
What is the resistance of the ideal ammeter?
Zero
What is the resistance of the ideal voltmeter?
Infinite
Define EMF
The potential difference across a cell when no current is drawn
Define resistivity
RA/l , where R is the resistance of the material of length l, and A is the cross sectional area
State the significance of the critical temperature of a material
The maximum temperature where a material has 0 resistivity
Define the volt
1 joule per coulomb
What is meant by a non-ohmic component?
A component which does not have a constant resistance
Why is a filament lamp most likely to fail as it is switched on?
The resistance is lower (due to lower temp)
So the initial current will be larger
What effect does reversing a cell have?
Reverses direction of the current
OR
cancels out pd with another cell
