Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
19 Cards in this Set
- Front
- Back
|
ammeter
|
measures electric current (the flow of electrons) - connected in series
|
|
|
ampere
|
the unit used to measure current - symbol = A
|
|
|
voltage
|
is a measure of the amount of energy supplied by the power source
|
|
|
voltmeter
|
measures voltage - connected in parallel
|
|
|
volts
|
the unit used to measure voltage - symbol = V
|
|
|
transformer
|
changes the voltage supplied to a device - eg 240 V MAINS reduced to 19V for a laptop
|
|
|
wet cell
|
2 different metal electrodes and an electrolyte solution eg car battery - acid and metal electrodes
|
|
|
electrode
|
metal conductor
|
|
|
electrolyte
|
fluid that conducts electricity
|
|
|
dry cell
|
contain a conducting paste, and electrodes - doesn't leak
|
|
|
photovoltaic cells
|
contain semi-conducting silicon crystals - sunlight knocks electrons off the crystal and they are used to create a current.
|
|
|
Resistance
|
As electrons pass along a wire, their progress is restricted by the atoms they encounter. Energy is lost as heat or light. Too much resistance and the wire will melt creating a fire.
|
|
|
Resistance factors
|
1 - type of material - metals provide little resistance. 2 - as the length of the wire increases, then so does the resistance. 3 - as the diameter of the wire increases, the resistance decreases.
|
|
|
Conductors
|
Metals are conductors - the offer very little resistance. Copper and aluminium are the better ones.
|
|
|
Insulators
|
Have such a high resistance, that no current is possible - rubber, plastics, wood glass and ceramics.
|
|
|
Ohm's Law
|
V = I R where
|
|
|
V
|
is voltage in Volts
|
|
|
I
|
is current in Amps
|
|
|
R
|
is the resistance in Ohms
|
