electricity Flashcards
what is emf
the total work done by a cell per coloumb of charge
what is ohm’s law
the pd across a conductor will be proportional to current as long as physicial conditions remain constant
what is the voltage across components that have work done on them by the current called
The potential difference
what is the terminal potential difference
the voltage across the terminals of a battery
what can internal resistance be thought of as
the resistance to the flow of current inside the power supply itself
how is resitance related to length
resistance is proportional to length
how is resistance related to area
resistance is inversly proportional to area
what is the relationship between a thermistor and increasing temperature
the resistance of the thermistor decreases
what is the relationship of an LDR and increasing light intensity
the resistance of the LDR increases
how would you measure the emf of a battery/cell
voltmeter across the terminals of the cell with nothing else connected to it
why must a voltemeter have very high resistance
so there is virtually no current
what is resistance
a measure of how difficult it is for charge carriers to pass through a component
what happens to the resistance of a metal conductor when it’s temperature increases
it’s resistance increases when it’s temperature increases
what is a superconductor
a material with zero resistivity at or below critical temperature
what is the temperature coefficient of a semi-conductor
negative temperature coefficient resistance decreases with increasing temperature
what is the current law at junctions
at any junction in a circuit, the total current leaving the junction is equal to the total current entering the junction
what is the rule for current entering a component for components in series
the current entering a component is the same as the current leaving the component
what is the rule for current passing through two or more components in series
current passing through two or more components in series is the same through each component
what is the net emf of two cells in opposite directions in series
the differences between the cells
what is the net emf of two cells in the same direction in series
the sum of the invdividual emfs of the cells
what is a potential divider
it consists of two or more cells in series with each other
with a source of fixed potential difference
what are three uses of a potential divider
to supply a pd which is fixed at any valuse between zero and the source pd
to supply a variable pd
to supply a pd that varies which a physical condition such as pressure or temperature
what is the ratio of pds across resistors in a potential divider equal to
the ratio of pds across each resistor is equal to the resistance ratio of the two resistors
what is the pd across components in parallel like?
the pd across components in parallel is the same
what the total pd across components in series equal to
the total pd across components in series is equal to the sum of the individual pds of the components
