Electrical Concepts Quiz
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Questions and Answers

What does a negative absorbed power indicate about an electrical element?

  • It has zero power.
  • It is consuming energy.
  • It is malfunctioning.
  • It is a source of energy. (correct)

    • The law of conservation of energy states that energy can be created or destroyed.

    False

    What is the unit of measure for energy?

    joules

    The power absorbed or supplied in a circuit must satisfy the condition $ ext{ } ext{sum of all powers} = $______

    <p>0</p> Signup and view all the answers

    Match the following elements with their computed power:

    <p>$P_a$ = -1200 W $P_b$ = -1080 W $P_c$ = 100 W $P_d$ = -10 W $P_e$ = 90 W $P_f$ = 500 W $P_g$ = 480 W $P_h$ = 1100 W</p> Signup and view all the answers

    What is the definition of current?

    <p>The measure of the rate at which charge is moving past a given reference point</p> Signup and view all the answers

    The direction of current flow is unimportant in electrical circuits.

    <p>False</p> Signup and view all the answers

    What is the relationship between current (i) and charge (q) over time (t)?

    <p>i = dq/dt</p> Signup and view all the answers

    A direct current (dc) is a current that remains ______ over time.

    <p>constant</p> Signup and view all the answers

    Match the type of current with its description:

    <p>DC = Remains constant with time AC = Reverses direction with time Current = Rate of flow of charge Charge = Amount of electricity stored</p> Signup and view all the answers

    What unit is used to measure current?

    <p>Amperes</p> Signup and view all the answers

    In a circuit, positive and negative ions flow in the same direction.

    <p>False</p> Signup and view all the answers

    If a current of 5 A flows for 10 seconds, how much charge has accumulated at the terminal?

    <p>50 C</p> Signup and view all the answers

    What is the unit of energy or work?

    <p>joule (J)</p> Signup and view all the answers

    Electric potential is measured in volts.

    <p>True</p> Signup and view all the answers

    What percentage of the final grade does the final exam account for?

    <p>40%</p> Signup and view all the answers

    What is the symbol for electric resistance?

    <p>Ω</p> Signup and view all the answers

    Electric capacitance is measured in __________.

    <p>farad (F)</p> Signup and view all the answers

    In an electric circuit, electrical effects occur instantaneously throughout a system.

    <p>True</p> Signup and view all the answers

    What are the three assumptions made in circuit theory?

    <p>Effects happen instantaneously, net charge is zero, no magnetic coupling.</p> Signup and view all the answers

    Match the following prefixes with their corresponding power of ten:

    <p>kilo = $10^{3}$ milli = $10^{-3}$ micro = $10^{-6}$ giga = $10^{9}$</p> Signup and view all the answers

    The basic unit for measuring electric current in the International System of Units is the ______.

    <p>ampere</p> Signup and view all the answers

    What relationship describes the voltage in a circuit?

    <p>v = dw/dq</p> Signup and view all the answers

    A voltage cannot exist between terminals if no current is flowing.

    <p>False</p> Signup and view all the answers

    Match the following basic units with their corresponding symbols:

    <p>Length = m Mass = Kg Time = s Electric current = A</p> Signup and view all the answers

    What is the primary unit of power?

    <p>watt (W)</p> Signup and view all the answers

    Which of the following best describes a lumped-parameter system?

    <p>A system where effects happen instantaneously.</p> Signup and view all the answers

    In a balanced circuit, the net charge on every component is always positive.

    <p>False</p> Signup and view all the answers

    Name one recommended reference book for this course.

    <p>Electric Circuits, 8th edition by J.W. Nilsson and Susan A. Riedel.</p> Signup and view all the answers

    What is the formula for charge accumulation due to current flow?

    <p>$q(t) = extcolor{red}{igg floor}_{0}^{t} i(x)dx$</p> Signup and view all the answers

    A current of 5 A accumulates 50 C of charge in 10 seconds.

    <p>True</p> Signup and view all the answers

    What is the definition of power in electrical circuits?

    <p>Power is the time rate of expending or absorbing energy.</p> Signup and view all the answers

    Power is calculated using the formula __________.

    <p>p = vi</p> Signup and view all the answers

    What happens to power when the charge moves through a rise in voltage?

    <p>Power is delivered to the circuit.</p> Signup and view all the answers

    Match the following terms with their descriptions:

    <p>Current = Flow of electric charge Voltage = Electric potential difference Power = Rate of energy transfer Charge = Electric property of particles</p> Signup and view all the answers

    The total accumulated charge at time t is given by the integral $ extcolor{blue}{igg floor}_{0}^{t} i(x)dx$. When $i=5 A$, the charge becomes __________.

    <p>5t</p> Signup and view all the answers

    If power is negative (p < 0), it indicates that energy is being supplied to the circuit.

    <p>False</p> Signup and view all the answers

    Study Notes

    Basic Electricity & Electronics - Circuit Variables

    • A circuit is a mathematical model approximating an actual electrical system.
    • Circuit theory is used, instead of electromagnetic field theory.
    • Three assumptions guide the model:
      • Electrical effects happen instantly throughout the system (lumped-parameter).
      • The net charge on every component is zero.
      • There's no magnetic coupling between components.

    Course Specifications

    • Assessment Methods:

      • Final Exam: 40%
      • Mid-term Exam: 20%
      • Tutorial Quiz: 10%
      • Lecture Quiz: 10%
      • Semester Work: (percentage not specified)

    • Essential Books:

      • Fundamental Electrical and Electronic Principles by Christopher R. Robertson (3rd edition, 2008)
      • Basic Engineering Circuit Analysis by J. Irwin and R. Nelms (10th edition, 2011)

    • Recommended Books:

      • Electric Circuits by J. W. Nilsson and Susan A. Riedel (8th edition, 2008)

    Problem Solving

    • Identify given and required information.
    • Sketch a circuit diagram or visual model.
    • Consider various solution approaches.
    • Select a method.
    • Calculate a solution.
    • Use creativity.
    • Test the solution.

    Balancing Power

    • Electrical source (a and b)
    • Wires (c, d, and e) carry current from the source.
    • Devices (f, g, and h) utilize electrical power (lamps, TVs, etc.)

    The International System of Units (SI)

    • Length: meter (m)
    • Mass: kilogram (kg)
    • Time: second (s)
    • Electric current: ampere (A)
    • Thermodynamic temperature: kelvin (K)
    • Amount of substance: mole (mol)
    • Luminous intensity: candela (cd)

    Derived Units in SI

    • Frequency: hertz (Hz), 1/s
    • Force: newton (N), kg ⋅ m/s²
    • Energy/work: joule (J), N ⋅ m
    • Power: watt (W), J/s
    • Electric charge: coulomb (C), A ⋅ s
    • Electric potential: volt (V), J/C
    • Electric resistance: ohm (Ω), V/A
    • Electric conductance: siemens (S), A/V
    • Electric capacitance: farad (F), C/V
    • Magnetic flux: weber (Wb), V ⋅ s
    • Inductance: henry (H), Wb/A

    Standardized Prefixes

    • Units of 10 (powers): atto (a), femto (f), pico (p), nano (n), micro (µ), milli (m), centi (c), deci (d), deka (da), hecto (h), kilo (k), mega (M), giga (G), tera (T)

    Example #1

    • Signal travels in cable at 80% speed of light.
    • Calculate cable length (inches) representing 1 nanosecond (ns).

    Voltage and Current

    • Charge is bipolar (positive/negative).
    • Electric charge exists in discrete quantities (integral multiples of the electronic charge: 1.6022 × 10⁻¹⁹ C).
    • Electrical effects are due to charge separation (voltage) and charge motion (current).

    Voltage

    • Separating positive and negative charges requires energy (w).
    • Voltage (v) is the energy per unit charge.
    •  1 volt is equal to 1 joule/coulomb (J/C).
    • Mathematically, voltage is defined as v = dw/dq

    Signs of the Terminals

    • A plus sign in terminal 1 indicates terminal 1 is positive with respect to terminal 2.
    • Terminals have a voltage even with no current flow.

    Example #2

    • (a, b) Terminal 2 is positive with respect to terminal 1.
    • (c, d) Terminal 1 is positive with respect to terminal 2.
    • Voltage can exist independent of current flow.

    Notes

    • Plus-minus signs in voltage expressions are conventions, not actual polarities.
    • Voltage definitions must include positive and negative signs.

    Current

    • Current (i) is the rate at which charge (q) moves past a given point.
    • Measured in amperes (A). Charge in coulombs (C). Time in seconds (s). 1 A = 1 C/s.
    • Current has a numerical value and a direction.
    • Mathematically, i = dq/dt.

    The Direction of Current Flow

    • Current direction depends if positive or negative ions are moving

    Direction is Important!

    • The direction of the arrow is a fundamental part of the current definition.

    DC and AC

    • Direct Current (DC): constant current.
    • Alternating Current (AC): current direction changes with time (sinusoidal variation).

    Example #3

    • A 5 A current begins at t=0.
    • Derive the charge expression for t>0.
    • Calculate accumulated charge at t=10 seconds.

    Positive Value

    • Voltage drop from terminal 1 to terminal 2.
    • Voltage rise from terminal 2 to terminal 1
    • Positive charge flowing from terminal 1 to terminal 2

    Negative Value

    • Voltage rise from terminal 1 to terminal 2.
    • Voltage drop from terminal 2 to terminal 1.
    • Positive charge flowing from terminal 2 to terminal 1.

    Power and Energy

    • Power (p) is the time rate of expending or absorbing energy (w).
    • Mathematically, p = dw/dt = dq/dt · v = i · v.
    • Units: Power in watts (W), energy in joules (J). Time in seconds (s), charge in coulombs (C), voltage in volts (V), current in amperes (A).

    Positive Sign Convention

    • The algebraic sign in power calculations depends on the direction of current and voltage.
    • Positive charges moving through a voltage drop lose energy, and moving through a voltage rise gain energy.

    Example #4

    • Positive power indicates power delivery to circuit.
    • Negative power indicates power extraction.
    • Calculate power absorbed by each circuit element.

    Solution for Example #4

    • Calculating power absorbed by each circuit element.
    • Consider the directions of current and voltage when evaluating power.

    Balancing Power

    • The law of conservation of energy dictates that the sum of powers in a circuit equals zero.
    • Energy is the capacity for work and is measured in joules (J).

    Example #5

    • Calculate the power absorbed by each element in the given circuit.
    • Determining voltage and current for each component.

    Example #5 answer

    • Applying the power formula (P = VI) for each circuit element, with correct current and voltage signs and direction.
    • Calculate the power absorbed by each element.

    Summary

    • Review of voltage, current, ideal circuit elements, passive sign convention, and power.

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    Basic Electricity & Electronics PDF

    Description

    Test your knowledge on fundamental electrical concepts including current, power, and energy measurements. This quiz covers essential definitions, laws, and calculations necessary for understanding electrical circuits. Perfect for students studying electrical engineering or physics.

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