physics - electricty Flashcards
what is an electrical current
flow of electric charge measured in amps
formula connecting flow of charge , current and time
flow of charge=current times time
Q=IT
What happens to current in a series circuit
current has the same value at every point
what is needed for a current to flow
source of potential difference
electrons
closed circuit
what is an electrical conductor
a material that allows electric currents (flow of electric charge) to pass through it
what is an electrical conductor
a material that allows electric currents (flow of electric charge) to pass through it.
All metals are electrical conductors
What are electrical insulators
a material that doesn’t allow electric currents to pass through it.
plastic and glass are electrical insulators
what do electrical conductors have that electrical insulators do not
lots of charges that are free to move and carry a current. In a metal the charges that are free to move are electrons
What is potential difference
the difference in the amount of energy that are charge carriers have between two points in a circuit. Measured in volts. The energy is transferred to the electrical components in the circuit when the charge carriers pass through them
formula relating voltage , charge and energy
voltage x charge = energy transferred
what is resistance
resistance is a measure of how difficult it is for a current to flow through a component. measured in ohms
if the resistance is increased and the pd is constant then the current will
decrease
what does the constant slope of a current-voltage graph tell us
the resistance is constant
what is a diode
a component that only allows current to flow through it in one direction
what is a thermistor
component where resistance changes with temperature. Usually increasing temperature, decreases resistance. we can use a thermistor to turn a heater off when a house reaches a certain temperature
what are LDRs
Light dependent resistors - restistnace changes with light intensity
formular relating power, current and PD
power=current x potential difference
P=IV
what is power
the rate of energy transfer to a component
how do you work out total energy transfer
total energy transferred = power x time
e=pt
What is an ohmic conductor
An Ohmic conductor is a conductor that obeys Ohm’s Law
What happens to current through an Ohmic conductor
current through an Ohmic conductor is directly proportional to the potential difference across a resistor. This means that the resistance stays constant as the current changes
which quantity is constant in a complete series circuit
current
How is the total potential difference found in series circuit
adding up each components individual voltages
what are the key features of series cells
all components are attached in rows
the current is equal everywhere in the circuit
the voltage across each component is different
the sum of the voltages across each component is the total battery voltage
