electricity Flashcards
charge
current x time
difference between alternating current and direct current
alternating current - continuously changes direction e,g main electricity
direct current - current flows in 1 direction only e.g cells, battery
conventional current
flowing from positive to negative
potential difference
voltage
resistance
r = voltage / current
increased resistance = reduces the current
resistance facts
resistance is directly proportional to length of wire
resistance is inversely proportional to diameter of wire
power
voltage x current
energy transferred
voltage x current x time
voltage
current x resistance
work done
voltage x charge
units used
power x time
in a series circuit
current is the same everywhere
voltage of individual components adds up to the total voltage
total resistance is the sum off all the individual components’ resistance
in a parallel circuit
voltage is the same everywhere
current of individual components adds up to the total current
combined resistance of two resistors in parallel is less than that of either resistor by itself
what is variable potential divider
uses a variable resistor to take portion of cells voltage
to be delivered to a separate circuit - amount of voltage delivered can be altered by varying the resistors
equation for two resistors used as a potential divider
r1/r2 = v1/v2
rectifier
a component used to change an alternating current into a direct current
diode
allow current to flow in 1 direction and used to produce a direct current from an alternating current
LDR
as light intensity increases, resistance decreases
used in circuits as an input transducer
when placed in potential divider to deliver voltage to a lamp , the lamp will come on when its dark.
Thermistors
resistance decreases as temperature increases
- used as input transducer in circuits needed to be sensitive to temperature e.g fire alarms
- thermistor is placed in a potential divider to deliver high potential difference in high temperature
- attached to a relay high voltage is used to turn on an electromagnet
increase the size of the induced current
- stronger magnets
- stronger magnetic field
- move wire faster
- wrap wire into a coil
electromagnetic induction
if a wire is moved into a magnetic field at right angles, voltage is induced
and if connected up to a complete circuit
- current is induced
what dictates the direction of the induced emf
it opposes the charge causing it
- e.g bar magnet approaches wire carrying a current which has turned into a temporary magnet
- this temporary magnet repels bar magnet approaching
