Electricity Definitions Flashcards
(13 cards)
K’s 1st law
Due to conservation of charge.
Total current entering junction is equal to total current leaving it
Mean drift velocity
Average velocity of electron passing through object
(Proportional to current, Inversely proportional to charge carriers and area)
EMF
• Energy per unit charge supplied by a source
• Energy transferred to charge carriers
• Energy transformed to electrical
• Charges gain energy
• Work done on charges
Pd
• Energy transferred by the charge carriers as they move through the component
• Energy transformed from electrical
• Charges loses energy
• Work done by charges
Resistance and resistivity
Resistance- measure of how difficult it is for current to flow
Resistivity- measure of how difficult it is for charge to flow
K’s 2nd law
Due to conservation of energy. Sum of pd in closed loop equal to sum of emf
Lost volts
Difference between emf and terminal voltage
Equal to pd across internal resistance
Terminal voltage
Pd across terminal.
Equal to emf- lost volts
Thermistor
• As temp increases, resistance decreases
LDR
• as light intensity increases, resistance decreases
Explain V in terms of distance of wire
• As d increases R of wire and load resistor increases
~ gets bigger share of emf
• I decreases so less emf lost inside battery
• due to internal resistance
Describe effect on ammeter voltmeter when NTC thermistor heated.
Ammeter and thermistor in series,
Voltmeter across thermistor
• temp of thermistor increased
• which provides more electrons sufficient energy
• so resistance decreases
• ammeter reading increases
• pd reading stays same
Explain reading voltmeter when temp of NTC thermistor increases
Resistor, variable resistor and thermistor in series
Voltmeter across resistor
• as temp increases resistance decreases
• share of emf decreases
• fixed resistor has increase pd across it
• reading on voltmeter increases
