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p3 (static electricity (always electrons (negative charges) that move,…
p3
static electricity
two materials rubbed together, electrons transferred from one to the other
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electrons can't flow in insulators, positive static charge left on object that lost electrons, negative static charge on object that gains electrons
always electrons (negative charges) that move, direction of electron transfer depends on materials
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electric fields
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closer lines, stronger field and force
when two charged objects interact, force is produced
repulsion and attraction
like charges repel, opposite attract
electrically charged objects exert force on each other, forces get weaker with distance
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testing charge
electrically charged objects attract small neutral objects, eg scraps of paper to charged rod
if rod is positively charged it attracts electrons, if it's negatively charged it repels electrons
gives surface of paper close to the rod an opposite charge to the rod so they are attracted
current
rate of flow of electric charge (electrons) around the circuit
only flows through electric component with potential difference and if it's closed
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potential difference
driving force, pushed circuit round
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IV graphs
component, ammeter and variable resistor in series, voltmeter in parallel around the component under test
vary resistor in variable resistor, alters current and pd in component
take readings from ammeter and voltmeter to see how pd varies as current changes
symbols
LED = circle with triangle and line and two arrows coming out
resistor = rectangle
variable resistor = rectangle with arrow
diode = circle with triangle and line
LDR = circle with rectangle and two arrows going in
thermistor = rectangle and hockey stick
ammeter
measure current flowing through the component
must be in series with the component
can be anywhere in series in the main circuit but never in parallel like the voltmeter
voltmeter
measures potential difference across the component
must be in parallel with component under the test, not variable resistor or battery
so can compare energy of charge before and after passing
high pd means high current
greater resistance, smaller current
in a closed loop, current is the same at any point