4A4 Simple and Combination Circuits Flashcards
Explore the different kinds of circuits, including how they apply to laws and power.
Define:
Electric circuit
A closed loop of electric elements where electric charges flow.
It has a source of electric charges that carry electric potential energy to other circuit components.
What are the four main components of a basic electric circuit?
- Power source (AC or DC)
- Load (such as a light bulb)
- Conductive path (wires)
- Switch
Additional components like resistors and capacitors can control current and voltage.
What is the function of a load in an electric circuit?
Converts electric potential energy to another form, such as light, heat, or mechanical motion.
Examples include bulbs, resistors, capacitors, and inductors.
Define:
EMF
Electromotive Force
Energy supplied per unit charge by a power source; measured in volts (V).
## Footnote
It’s the maximum voltage of a source when no current flows—the open-circuit potential.
Fill in the blanks:
In a circuit, the conventional current flows from the ______ terminal to the ______ terminal of the power source.
positive; negative
Conventional current assumes the flow of positive charges, even though electrons actually move in the opposite direction.
What happens in a series circuit when one component fails?
The circuit is opened and cannot work.
This occurs because the components are connected like a chain.
Define:
Series circuit
A circuit in which components are connected end-to-end, providing a single path for current.
In series circuits, the current is the same through all components, but the voltage divides.
Define:
Parallel circuit
A circuit in which multiple paths are available for current to flow.
Each component is connected across the same two points of the circuit.
True or false:
In a parallel circuit, the voltage is the same across all branches.
True
The voltage remains constant across all parallel components, but the current divides.
Explain why combination circuits are useful in practical applications.
They combine series and parallel circuits, allowing control over both current and voltage.
These circuits are used in systems like home wiring, where some parts need shared current (series) and others need independent paths (parallel).
In a series circuit, how does adding a component affect the total resistance?
It increases the total resistance of the circuit.
This causes the total voltage to be more divided among the components.
What type of circuit is most common in home electrical systems?
Parallel circuit
Parallel circuits ensure that each device receives the same voltage and can operate independently.
What happens to the current if one resistor fails in a series circuit with three resistors?
The current stops flowing.
In a series circuit, any break stops the entire current because there’s only one path.
What happens when you remove a bulb from a parallel circuit?
The total resistance increases, and total current decreases.
However, the remaining bulbs still receive the full voltage.
How is current affected in a parallel circuit when more branches are added?
The total current increases.
This occurs because the circuit’s overall resistance decreases as more parallel paths are added.
True or false:
Series circuits are more energy-efficient than parallel circuits.
False
Parallel circuits are often more energy-efficient and practical for distributing power in systems.
Why do Christmas lights often use parallel circuits instead of series circuits?
If one bulb burns out, the others remain lit.
In parallel circuits, each bulb has an independent connection to the power source.
How does Ohm’s Law apply to a series circuit?
Ohm’s Law can determine the total resistance by adding individual resistances.
In a series circuit, the current is the same throughout. The total voltage is divided among the components based on their resistances.
Explain how Ohm’s Law applies to a parallel circuit.
Ohm’s Law can be applied to each branch individually because the voltage across each branch is the same.
The total current is the sum of the currents through each branch.
Define:
Equivalent resistance
Single resistance that could replace all resistors in a circuit without changing the total current or voltage.
It depends on whether it is a parallel or series circuit.
How do you find the equivalent resistance in a series circuit?
Sum the individual resistances:
Req =R1+R2+R3+…
The same current flows through all resistors in a series circuit.
How do you find the equivalent resistance in a parallel circuit?
Sum of the reciprocal individual resistances:
1/Req = 1/R1 + 1/R2 + 1/R3 + ⋯
The voltage across each resistor is the same in a parallel circuit.
True or false:
Adding more resistors in parallel reduces the total resistance.
True
This happens because more pathways for current are created.
A circuit has three resistors: 4Ω, 6Ω, and 8Ω connected in series. What is the total resistance?
18Ω
4Ω+6Ω+8Ω=18Ω
True or false:
The equivalent resistance in series is always greater than any individual resistance.
True
This follows directly from the sum rule of resistances.
Define:
Equivalent capacitance
Single capacitance that could replace multiple capacitors in a circuit while maintaining the same electrical behavior.
It depends on whether it is a parallel or series circuit.
What happens to equivalent capacitance when capacitors are placed in parallel?
The equivalent capacitance increases.
This is because the equivalent capacitance is the sum of the individual capacitances.
What is the formula for equivalent capacitance in parallel?
Ceq = C1 + C2 + C3 + ⋯
This formula indicates that you sum the capacitances of all capacitors in parallel.
Fill in the blank:
In a series circuit, the total capacitance is ______ than the smallest individual capacitance.
less
In series, 1/Ceq = 1/C1 + 1/C2 + 1/C3 + ⋯
How do you find the equivalent capacitance of a complex circuit?
- Find the equivalent capacitances of isolated pieces of the circuit.
- Redraw the circuit with new equivalent capacitors.
- Repeat until a single capacitor is obtained.
This method allows for systematic simplification of complex circuits.
What happens to equivalent capacitance when capacitors are placed in series?
The equivalent capacitance decreases.
In series, the equivalent capacitance is less than the smallest individual capacitance.
What is the effect of adding capacitors in parallel on the total capacitance?
It increases compared to individual capacitances.
For example, three capacitors with capacitances of 10μF, 3μF, and 8μF yield an equivalent capacitance of 21μF.
What is the effect of adding capacitors in series on the total capacitance?
It decreases compared to individual capacitances.
For instance, three capacitors with capacitances of 10μF, 3μF, and 8μF yield an equivalent capacitance of approximately 1.79μF.
Explain why equivalent capacitance is lower in series than in parallel.
In series, the effective separation between capacitor plates increases, lowering total capacitance.
In parallel, the effective plate area increases, boosting capacitance.
Explain why capacitors are often connected in parallel in power supply circuits.
To store more charge and provide a stable voltage.
Higher capacitance in parallel improves filtering in power supplies.
If two 10 μF capacitors are connected in series, what is their equivalent capacitance?
5 μF
1/Ceq = 1/10μF + 1/10μF
Why are capacitors ideal for use in timing circuits?
They store and release charge at predictable rates.
This property allows capacitors to control timing intervals.
Define:
Kirchhoff’s Current Law (KCL)
The total current entering a junction must equal the total current leaving a junction.
This law is based on the conservation of electric charge.
Define:
Kirchhoff’s Voltage Law
(KVL)
The change in potential around a closed loop must be zero.
This law is derived from the conservation of energy.
True or false
Kirchhoff’s Voltage Law applies only to series circuits.
False
KVL applies to any closed loop, regardless of circuit configuration.
Define:
Nodes
in Kirchhoff’s laws
They are connections of two or more current-carrying routes.
Kirchhoff’s laws apply to these junction points in circuits.
What is the first step in solving problems using Kirchhoff’s laws?
Label the current in each branch of the circuit and label the direction.
This helps in identifying unknowns and applying the laws correctly.
What are the limitations of Kirchhoff’s circuit laws?
They lose validity in high-frequency AC circuits.
The laws depend on assumptions about constant net charge and stable magnetic fields, which may not hold in such cases.
Explain why KCL is useful when analyzing complex circuits.
It helps determine the current at each junction.
KCL simplifies current distribution analysis in circuits.
What does Kirchhoff’s Voltage Law imply about potential differences in a closed loop?
They cancel each other out to zero.
The total energy gained equals the total energy lost.
True or false:
Kirchhoff’s Voltage Law can be applied to analyze circuits with multiple power sources.
True
KVL is valid regardless of the number of power sources in the loop, as long as all voltage gains and drops are accounted for.
If I₁ flows into a junction and I₂ and I₃ flow out, how is Kirchhoff’s Current Law expressed?
I₁ = I₂ + I₃
Based on charge conservation: total inflow = outflow at a junction.
Why is KVL essential in power distribution networks?
It ensures that voltage levels are consistent and manageable.
This prevents voltage imbalances and ensures circuit stability.
True or false:
KCL states that current can accumulate at a junction.
False
Current cannot accumulate due to charge conservation.
How does KCL apply to parallel circuits?
The sum of currents through each branch equals the total current entering the circuit.
Each branch carries part of the total current.
True or false:
Power is inversely proportional to voltage.
False
Power increases with voltage if current is constant.
Explain why power transmission lines use high voltage.
To reduce current and minimize power loss due to resistance.
Lower current reduces resistive heating losses.
What is the difference between real power and reactive power?
- Real power does useful work.
- Reactive power maintains voltage levels in AC systems.
Real power is measured in watts; reactive power in VARs (volt-ampere reactive).
How is power calculated in a series circuit?
It is calculated as P=I²R, where the current is constant throughout the circuit, and the total resistance is the sum of individual resistances.
The total power is the sum of the power dissipated in each resistor.
True or false:
In a parallel circuit, the total power is the sum of the power consumed by each branch.
True
Each branch operates independently with the same voltage across them.
Fill in the blank:
In a ______ circuit, the power dissipated by each resistor can be calculated as P=V²/R, where voltage across each branch is the same.
parallel
Power dissipation in each branch depends on the resistance.
True or false:
A 100-watt bulb uses more energy in one second than a 60-watt bulb.
True
Higher power ratings consume energy faster.
