circuits, voltage, current and resistance Flashcards
what does an ammeter do?
measures current
what does a voltmeter do?
measures the voltage
what does a switch do?
breaks the circuit
what does a resistor do?
used to limit the current that flows
what does a diode do?
allows current to flow
what does a lamp do?
changes electrical energy to light energy
what does a cell do?
provides the push of an electrical supply
what is current?
rate of flow of electrons in a circuit
what is current measured in?
amps (A)
how is an ammeter connected?
in series
what is voltage?
push force in a circuit
what is voltage measured in?
volts (V)
how is a voltmeter connected?
in parallel with component
what is a series circuit?
different components follow one after the other
one path for current to flow
what is the current like in a series circuit?
the same
what happens when you unscrew a bulb?
circuit breaks
what happens in series circuits when you add bulbs?
decreases current and brightness of each bulb
what is a parallel circuit?
components are side by side
more than one path for current to flow
what is the current like in a parallel circuit?
some goes through one lamp and some goes through others
it splits and joins at junctions
what are the advantages of a parallel circuit?
independent operation of bulbs
what do all the bulbs have?
the same brightness
what is resistance?
the greater the resistance the less current flows
less resistance, more current
how does length affect resistance?
more atoms, more collisions per second, larger resistance
how does temperature affect resistance?
atoms vibrate more, more collisions, larger resistance
how does thickness affect resistance?
more gaps, less collisions, smaller resistance
how does material affect resistance?
conductors - low resistance
insulators - high resistance
what is ohms law?
voltage is directly proportional to current as long as temperature is constant
what happens to resistance when you add components in series?
increases
what happens to resistance when you add components in parallel?
decreases
what are the I V characteristics if a resistor?
voltage is directly proportional to current
resistance is constant when a wire is at constant temperature
what are the I V characteristics of a bulb/ lamp?
as voltage increases, current increases less and less
resistance is increasing because bulb is getting hot
what are the I V characteristics of a diode?
diode has low resistance after a certain value
current increases dramatically as he voltage increases very little
resistance decreases
what are the uses of thermistors?
fire alarms. Increased temperature would reduce resistance in a circuit. The current will increase and alarm goes off
what are uses of an LDR?
night lights. When brightness decreases, resistance increases and this causes light to turn on
what is power?
rate at which electrical energy is transferred to other forms of energy per second
what is power measured in?
Watts (W)
