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Questions and Answers
The direction of current and the polarity of voltage in Ohm’s Law can be disregarded.
The direction of current and the polarity of voltage in Ohm’s Law can be disregarded.
True
A short circuit is a circuit element with resistance approaching infinity.
A short circuit is a circuit element with resistance approaching infinity.
False
Conductance is the ability of an element to resist electric current.
Conductance is the ability of an element to resist electric current.
False
A linear resistor has varying resistance.
A linear resistor has varying resistance.
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The resistance of a circuit element with zero voltage is always zero.
The resistance of a circuit element with zero voltage is always zero.
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The conductance of a resistor is always less than one.
The conductance of a resistor is always less than one.
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All resistors obey Ohm’s Law.
All resistors obey Ohm’s Law.
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A branch in a circuit can represent multiple two-terminal elements.
A branch in a circuit can represent multiple two-terminal elements.
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Two nodes connected by a short circuit wire constitute two separate nodes.
Two nodes connected by a short circuit wire constitute two separate nodes.
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A loop is a path in a circuit that does not start and end at the same node.
A loop is a path in a circuit that does not start and end at the same node.
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A network with b branches, n nodes, and l independent loops will satisfy the equation b=l+n+1.
A network with b branches, n nodes, and l independent loops will satisfy the equation b=l+n+1.
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Two elements are in series if they are connected to the same two nodes.
Two elements are in series if they are connected to the same two nodes.
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Elements in parallel are connected to different nodes.
Elements in parallel are connected to different nodes.
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A redrawn circuit can have a different number of nodes than the original circuit.
A redrawn circuit can have a different number of nodes than the original circuit.
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An independent loop contains all the branches in a circuit.
An independent loop contains all the branches in a circuit.
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A circuit can have multiple independent loops that share a common branch.
A circuit can have multiple independent loops that share a common branch.
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If we travel counterclockwise in a circuit, the signs of the voltages in KVL are the same as when we travel clockwise.
If we travel counterclockwise in a circuit, the signs of the voltages in KVL are the same as when we travel clockwise.
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Voltage sources in series add up to the algebraic sum of the individual voltages.
Voltage sources in series add up to the algebraic sum of the individual voltages.
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A circuit can contain two different voltage sources v1 and v2 in parallel without any restrictions.
A circuit can contain two different voltage sources v1 and v2 in parallel without any restrictions.
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Resistors connected in series have different currents passing through them.
Resistors connected in series have different currents passing through them.
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In a voltage divider, the smaller the resistance, the larger the voltage drop.
In a voltage divider, the smaller the resistance, the larger the voltage drop.
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In a 2-resistor circuit, the equivalent resistance is the sum of the individual resistances.
In a 2-resistor circuit, the equivalent resistance is the sum of the individual resistances.
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Parallel resistors have different currents passing through them.
Parallel resistors have different currents passing through them.
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The total current in a parallel circuit is shared by the resistors in direct proportion to their resistances.
The total current in a parallel circuit is shared by the resistors in direct proportion to their resistances.
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Elements in a circuit can never be connected in a way that they are neither in series nor in parallel.
Elements in a circuit can never be connected in a way that they are neither in series nor in parallel.
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The 5-Ω resistor and the 2-Ω resistor are in parallel in the given circuit.
The 5-Ω resistor and the 2-Ω resistor are in parallel in the given circuit.
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Kirchhoff's current law (KCL) states that the sum of the currents entering a node is less than the sum of the currents leaving the node.
Kirchhoff's current law (KCL) states that the sum of the currents entering a node is less than the sum of the currents leaving the node.
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Currents leaving a node can be regarded as positive in KCL.
Currents leaving a node can be regarded as positive in KCL.
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KCL can be applied to current sources in series.
KCL can be applied to current sources in series.
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Kirchhoff's voltage law (KVL) states that the algebraic sum of all voltages around a closed path is always positive.
Kirchhoff's voltage law (KVL) states that the algebraic sum of all voltages around a closed path is always positive.
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KVL can be applied in only one direction around a loop.
KVL can be applied in only one direction around a loop.
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The principle of conservation of energy is the basis for Kirchhoff's current law (KCL).
The principle of conservation of energy is the basis for Kirchhoff's current law (KCL).
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For a circuit with N resistors in parallel, the equivalent resistance is the sum of the individual resistances.
For a circuit with N resistors in parallel, the equivalent resistance is the sum of the individual resistances.
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Wye-Delta transformations are used only in three-phase networks.
Wye-Delta transformations are used only in three-phase networks.
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The delta to wye conversion rule is to add the resistors in the two adjacent Δ branches.
The delta to wye conversion rule is to add the resistors in the two adjacent Δ branches.
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Three-terminal equivalent networks can be used to simplify only series circuits.
Three-terminal equivalent networks can be used to simplify only series circuits.
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The equivalent resistance of a circuit with two resistors in parallel is the sum of the individual resistances.
The equivalent resistance of a circuit with two resistors in parallel is the sum of the individual resistances.
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A delta network can be transformed into a wye network without adding an extra node.
A delta network can be transformed into a wye network without adding an extra node.
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The resistance between each pair of nodes in the delta network is always different from the resistance between the same pair in the wye network.
The resistance between each pair of nodes in the delta network is always different from the resistance between the same pair in the wye network.
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Wye-Delta transformations are used to simplify only electrical filters.
Wye-Delta transformations are used to simplify only electrical filters.
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Study Notes
Ohm's Law
- States that voltage (V) is directly proportional to current (I) flowing through a resistor
- Mathematical form: V = I × R, where R is the resistance of the element
- Resistance (R) is measured in ohms (Ω) and is the ability of an element to resist electric current
- Direction of current and polarity of voltage must conform with the Passive sign convention
Classification of Resistors
- Linear resistors obey Ohm's law and have constant resistance
- Non-linear resistors do not obey Ohm's law
- Conductance (G) is the ability of an element to conduct electric current, measured in mhos ( ) or siemens (S)
- Conductance is the reciprocal of resistance: G = 1/R = I/V
Circuit Concepts
- A branch represents a single two-terminal element, such as a voltage source or a resistor
- A node is the point of connection between two or more branches
- A loop is any closed path in a circuit, formed by starting at a node and returning to the same node without passing through any node more than once
- Independent loops are loops that contain at least one branch not part of another independent loop
Kirchhoff's Laws
Kirchhoff's Current Law (KCL)
- States that the algebraic sum of currents entering a node (or closed boundary) is zero
- Mathematically, KCL implies: ΣI = 0
- Applies to current sources in parallel: the combined current is the algebraic sum of the current supplied by individual sources
Kirchhoff's Voltage Law (KVL)
- States that the algebraic sum of all voltages around a closed path (or loop) is zero
- Mathematically, KVL implies: ΣV = 0
- Applies to voltage sources in series: the combined voltage is the algebraic sum of the individual voltages
Series and Parallel Circuits
- Series circuits: elements share a single node and carry the same current
- Parallel circuits: elements are connected to the same two nodes and have the same voltage across them
- Voltage division: the source voltage is divided among resistors (in series) in direct proportion to their resistances
- Current division: the total current is shared by resistors (in parallel) in inverse proportion to their resistances
Wye-Delta Transformations
- Wye (Y) or Tee (T) network and Delta (Δ) or Pi (Π) network are three-terminal equivalent networks
- Used in three-phase networks, electrical filters, and matching networks
- Delta to Wye conversion: each resistor in the Y network is the product of the resistors in the two adjacent Δ branches, divided by the sum of the three Δ resistors
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Description
This quiz covers the fundamental principles of Ohm's Law, including the relationship between voltage, current, and resistance in direct current circuits.
