P3.2 Flashcards
What is a series circuit?
a series circuit is one in which the same charge passes through all components, so the current through each component is the same.
what is a parallel circuit?
a circuit in which the charge is split between branches
what two factors does the current in a circuit depend on?
potential difference
resistance
what equation should be used to calculate potential difference if current and resistance are known
V = I R
what is an Ohmic Conductor
a conductor for which current and potential difference are directly proportional
resistance remains constant as current changes
temperature must be constant
list four components for which resistance is not constant as current changes.
lamps
diodes
thermistors
LDRs
what is different about current flow through a diode?
the current only flows in one direction
resistance is very high in the other direction, preventing current flow
what happens to the resistance of a filament lamp as the temperature increases? why?
resistance increases
ions in metal have more energy, so vibrate more, causing more collisions with electrons as they flow through the metal, creating greater resistance
state what happens to the resistance of a thermistor as temperature increases
the thermistors resistance decreases
give an application for a LDR
street lamps or night lights
when light levels become low enough, the light gains sufficient current to turn on
give two examples of when a thermistor may be used
in a thermostat to turn a heater on below a certain temperature
in a freezer to turn on a cooler when the temperature becomes too high
state an equation linking energy transferred, charge flow and potential difference
Energy (joules) = charge(coulombs) x potential difference (volts)
state what happens to the resistance of a LDR as light intensity decreases
the LDR’s resistance increases
what are the two ways that a component can be connected in a circuit
series (same loop)
parallel( adjacent loop)
if two resistors are connected in series, what can be said about their total resistance?
their total combined resistance is equal to the sum of the two individual resistances
state an equation linking energy transferred, power and time.
Energy (joules) = power(watts) x time(seconds)
if two resistors are connected in parallel, what can be said about their combined total resistance?
their total resistance is less than the smallest of the two individual resistances.
how does the potential difference across two components vary when connected in series and parallel
series: total p.d is shared between each component
parallel: p.d across each component is the same
state two equations for the power of a circuit
P = I V
P = I^2 R
how should a voltmeter be connected in a circuit
in parallel to the component that you are measuring the potential difference for
how should an ammeter be connected in a circuit?
in series with branch you are measuring the current for
