Download Electric Circuits

Electric Circuits
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Series Circuits
Only ________________ for circuit current
_________________ is the same in all parts of circuit
Sum of _______________________ across circuit elements equals source emf
Total circuit resistance equals ______________ of separate resistances
Parallel Circuits
__________________________ conducting path for circuit current
Two or more components connected across two ______________________ in circuit
Currents in parallel branches vary __________________ with branch resistance;
Total current = ____________________________________________
Voltage drop is always _________________ across parallel branches
Parallel resistances add following ________________________:
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1
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  reciprocal of total resistance equals sum of reciprocals of
RT R1 R2 R3
individual resistances
For two parallel resistances the equation can be simplified: RT  RR11RR22
Circuit Networks
Combination of ___________________________________
To analyze, first find total resistance (RT), then ___________________________
To simplify resistance networks, replace several resistances with one ______________
resistance (Req)
Start with __________________ resistances and combine
Then collapse __________________________ into one equivalent resistance
Combine ___________________ resistances created by previous step
Continue until only one __________________________ resistance remains
Kirchhoff’s Rules
1. Algebraic sum of currents at any circuit junction equals zero
Total current flowing into a junction equal sum of currents leaving the junction;
___________________________________________
2. Algebraic sum of all voltage drops around a circuit loop equals zero
In a closed path around a circuit, voltage loss due to circuit elements equals voltage
gain produced by battery or other source of emf;
________________________________________________________________
Overload Protection
Homes have 120 volt lines from power company
Home circuits are connected in parallel
Each parallel branch _______________ total resistance, increasing _______________
in supply lines
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Lines can become __________________ causing heating and fire danger
Circuits protected by ______________ or ______________________ which open
circuit if current rises beyond certain value
• Protect against ______________________ where bare wires touch together
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Battery Cells
Wet cells: use _____________________ - car battery
Dry cells: use paste ____________________ - flashlight batteries
Primary cells: replaced when __________________ are used up
Storage cells: easily __________________
Fuel cells: New ____________________ added as needed
Combinations of Cells
Battery is combination of cells connected in series, parallel, or combination of both
Cells in series: cells connected + to -, as in a flashlight
Battery emf = __________ of cell emf’s;
Battery current = current of ________________, ___________________ throughout
Cells in ______________: neg. terminals all connected together and pos. terminals all
connected together
Battery emf = emf of _____________
Total current drawn by circuit is ______________________ among the cells;
Electrical Measurements
Voltmeter must be placed in ________________ with circuit element whose voltage
drop is being measured
Ammeter must be placed in ________________ so that all circuit current flows
through ammeter.
Never connect the ammeter in parallel like the voltmeter
Measuring Resistance
Resistance can be measured using a ______________ and ______________________
and calculating resistance using Ohm’s Law
Some error is introduced by the ___________________
____________________ uses this method
__________________________ gives more precise measurement