Electric Circuits Flashcards
What is the equation for electric current?
I=Δq/Δt
Units: C/s or A (Amps)
What is an Electric Current?
Moving electric charges; measures the amount of charge passing a given point every second
What does a battery do in a circuit?
It supplies the potential difference (voltage) needed to maintain a continuous flow of charge
What path does an electric charge take in a circuit?
Positive to negative
What is a Resistor?
Device whose function is to oppose the current of a circuit
What is an Ammeter?
Device that measures the current; used in series with a circuit
What is a Voltmeter?
Device that measures potential difference; used in parallel to a circuit
Is there an observable difference in readings of an ammeter when it is moved to a different location?
No
Is there an observable difference in readings of an voltmeter when it is moved to a different location?
No
What differences in readings of a ammeter/voltmeter are observable?
Difference in emf across the terminals of a battery
What is Electromotive Force (emf)?
Potential difference; voltage
Units: Volts
What is a Circuit?
A complete loop/circle of wire that allows for continuous flow of charge
What is Terminal emf?
First emf reflects the work done by the battery to move more change through the circuit and across terminals of the battery; total voltage; also known as internal emf
What is Resistance?
Electrical friction caused by the interaction of flowing electrons and molecules of a wire
What is resistance dependent on?
Temperature
What does an increase in temperature do to the resistance of a circuit?
Increases the current flow
What is Ohm’s Law?
If temperature is constant, as the voltage increases, a greater flow of current will be observed; direct relationship between voltage and current
What is the equation for resistance? (aka Ohm’s Law)
R=V/I or V=IR
Units: ohms (Ω)
What is the slope of a voltage vs current graph represent?
slope=resistance
R=V/I
What is Resistivity?
Measure of resisting power of a certain material to the flow of an electric current (ρ)
What is the equation for resistivity?
R=ρL/A
L=length of wire
A=area of cross section
Units (ρ)=Ω*m
What happens if a wire has a smaller cross section area? (R=ρL/A)
The resistance of the wire will increase
What happens if the length of the wire increases? (R=ρL/A)
The resistance of the wire will increase
What is the equation for the total power of a circuit?
P=ΔVI
Units: Watts (W)
What is equation for electrical energy?
E=Pt or E=WIt or E=I^2Rt
Units: Joules (J)
What is a Series Circuit?
A circuit consisting of two or more resistors sequentially placed within one circuit
What will happen if there is a break (ie. light bulb goes out) in a series circuit?
The entire circuit will shut down; the continuous path is broken
Is the current of a series circuit the same or different throughout the circuit?
The current is the same because there is only one circuit
Is the terminal emf (or voltage) of a series circuit the same or different throughout the circuit?
The voltage is different; it is equal to the sum of all the emf’s across all of the resistors
Where is there potential drop in a circuit?
Across each resistor
What is Potential Drop?
The amount of voltage loss that occurs through all or part of a circuit due to resistance; also known as voltage drop
What will happen to a series circuit if more resistors are added?
The electric current will decrease by increasing the resistance of the current, if the voltage is the same; as resistance increases, current decreases
What is the equation for the current of a series circuit?
I(total)=I1=I2=I3
Current is the same throughout
What is the equation for the voltage of a series circuit?
V(total)=V1+V2+V3
IR(total)=IR1+IR2+IR3
Voltage is different/shared
What is the equation for the resistance of a series circuit?
R(total)=R1+R2+R3
What is a Parallel Circuit?
A circuit consisting of two or more resistors connected across each other to a common point of potential difference
What happens if there is a break (ie. light bulb going out) in a parallel circuit?
The circuit does not go out because the current can flow to through the other path
Is the voltage of a parallel circuit the same or different throughout the circuit?
Same because each resistor is connected at a common potential point; voltage across each resistor is equal to the source voltage
What will happen in a parallel circuit if more resistors are added?
Will increase the effective circuit current by decreasing the circuit resistance; as resistance decreases, current increases
What is the equation for the voltage of a parallel circuit?
V(total)=V1=V2=V3
Voltage is the same throughout
What is the equation for the current of a parallel circuit?
I(total)=I1+I2+I3
V/R(total)=V/R1+V/R2+V/R3
Current is different/shared
What is the equation for the resistance of a parallel circuit?
1/R(total)=1/R1+1/R2+1/R3
What are Kirchhoff’s Circuit Laws (2)?
Junction Rule (current) and Loop Rule (voltage)
What is the Junction Rule?
The sum of currents flowing into a branch must equal the sum of currents leaving
What is the Loop Rule?
The sum of all emfs around a loop is equal to the sum of the potential drops around the loop
Where should an ammeter be placed in a circuit?
In series, right before or after the given resistor; an ammeter measures the current
Where should a voltmeter be placed in a circuit?
In parallel, across the given resistor; a voltmeter measures the voltage
