electricity Flashcards
100% on the eoy :) (21 cards)
current in a resistor result in…
electrical transfer of energy + increase in temp
bc: moving electrons collide w/ atoms in a resistor, atoms vibrate more rapidlly, increasing KE & overall temp
power =
the rate at which energy is transferred, current x voltage
energy transferred =
current x voltage x time
why is a series or parallel circuit more appropriate for particular apps? e.g domestic lighting
parallel circuit is best for domestic lighting as it allows independent control of individual lights, ensuring constant brightness
current depends on…
applied voltage and number of other components
current
the rate of flow of charge
resistance on current
resistance up = current down
LDRs illumination on resistance
illumination up = resistance down
thermosisters temp on resistance
temp up = resistance down
leds indicate…
current present
voltage =
current x resistance
charge =
current x time
current in solid metallic conductors is…
the flow of negatively charged electrons
why is current conserved at a junction in a circuit
at a junction, current ‘splits’ in order to take both paths. It is not dissipated, and instead comes back together when the two paths meet again
voltage =
energy transferred per unit charge passed
J/C
energy transfered (voltage)
charge x voltage
how are positive and negative electrostatic charges produced on materials by the loss and gain of electrons?
loss of electrons makes material positively charged
gain of electrons makes material negatively charged
e.g when perspex is rubbed it transfers electrons onto the cloth, so the perspex acquires a positive charge
electrostatic phenomena in terms of the movement of electrons
electrons can move from one object to another. When electrons transfer, static electricity is built up and + or - charges the object.
dangers of electrostatic chargers fuel running in an aircraft
fuel running =
friction
static
this ignites
(prevented by earthing w/ a conductor)
inkjet printers
Inkjet printers use two deflecting plates and ink droplets. The plates are one negative and one positive. Each spot of ink is charged, and the two plates use electrons to direct it. The plates are connected to a voltage supply that can change hundreds of times per second so that each drop falls into a particular position. This forms words or pictures.
photocopiers
Inside, there is a tuning drum. This turning drum is covered in selenium metal. Light is shone on the paper to be copied. The light parts of the paper reflect light onto the drum. The dark parts do not. The drum loses charge on the places the light reflects. Carbon powder called toner (negatively charged) gets blown and stuck to the still charged parts of the turning drum. The new paper gets pressed against the drum and picks up the ink.
