In an AC circuit, what is the phase difference between the voltage and current in a purely inductive circuit?
A 0 degrees
B 90 degrees
C 180 degrees
D 45 degrees
In a purely inductive circuit, the current lags the voltage by 90 degrees. This phase shift occurs due to the inductive reactance, which resists changes in current.
What is resonance in an electrical circuit?
A The point at which current is maximized
B The point where the inductive and capacitive reactances cancel out
C The point where power is maximized
D The point where impedance is minimized
Resonance occurs in an RLC circuit when the inductive reactance equals the capacitive reactance. At this point, the impedance of the circuit is minimized, and the current is maximized.
What is the primary function of a transformer?
A To step up or step down voltage
B To store energy
C To regulate current
D To filter signals
A transformer is used to change the voltage level in an AC circuit, either stepping it up (increasing voltage) or stepping it down (decreasing voltage), while keeping the power constant.
What is the role of a capacitor in an electrical circuit?
A To store energy in an electric field
B To provide constant current
C To store energy in a magnetic field
D To resist changes in current
A capacitor stores electrical energy in the form of an electric field between its plates. It is commonly used in filtering applications and energy storage.
What does the power factor of an electrical circuit represent?
A The ratio of real power to apparent power
B The total power consumed in the circuit
C The total voltage in the circuit
D The efficiency of a transformer
The power factor (PF) is the ratio of real power (active power) to apparent power in an AC circuit. A PF of 1 indicates perfect efficiency, where all the power is used effectively.
What is a feedback mechanism in electrical circuits?
A A method of increasing current flow
B A process that affects the output based on input changes
C A method of amplifying the signal
D A method of filtering signals
A feedback mechanism involves using the output of a system to influence the input. In electronic circuits, feedback is often used in amplifiers to stabilize or control the circuit’s behavior.
What is the purpose of electrical filters in circuits?
A To remove unwanted frequencies
B To store energy
C To step up voltage
D To regulate current
Electrical filters are used to allow certain frequencies to pass while blocking others. They are commonly used in signal processing, audio systems, and communication circuits.
What is the unit of inductance?
A Henry
B Ohm
C Farad
D Watt
Inductance is measured in henries (H), which is the unit that quantifies the ability of an inductor to store energy in a magnetic field.
What does an RLC circuit consist of?
A A resistor, inductor, and capacitor
B A resistor, capacitor, and transformer
C A resistor, transformer, and inductor
D A capacitor, transformer, and diode
An RLC circuit is composed of a resistor (R), inductor (L), and capacitor (C). These circuits are used in many applications, including filters, oscillators, and tuning circuits.
What is an equivalent circuit?
A A simplified representation of a complex circuit
B A circuit with identical components
C A circuit with an equal current throughout
D A circuit that stores energy
An equivalent circuit is a simplified model that represents the behavior of a more complex circuit using simpler components like resistors, capacitors, and inductors.
What is the basic unit of resistance?
A Ampere
B Volt
C Ohm
D Watt
The unit of resistance is the ohm (Ω). It measures the opposition to the flow of electric current in a conductor. One ohm is the resistance when one volt causes one ampere of current to flow.
In a series circuit, how is the current across each component?
A Different for each component
B The same for all components
C Higher in resistors
D Lower in capacitors
In a series circuit, the current that flows through each component is the same. This is because the current flows through each component one after the other without any branching.
What is the primary characteristic of a parallel circuit?
A The current is the same through all components
B The voltage is the same across all components
C The total resistance is the same as individual resistances
D The power is the same for all components
In a parallel circuit, the voltage across each component is the same. However, the current is divided among the components depending on their resistance.
What is the function of an inductor in an AC circuit?
A To store energy as electric field
B To store energy as magnetic field
C To block DC
D To convert AC to DC
An inductor stores energy in the form of a magnetic field when current passes through it. It resists changes in current flow, especially in AC circuits.
What does a capacitor do in an AC circuit?
A It resists changes in current flow
B It allows DC current to pass
C It stores energy in an electric field
D It generates voltage
A capacitor stores energy in the form of an electric field between its plates. In AC circuits, capacitors smooth voltage fluctuations and filter signals.
What is the role of a resistor in an electrical circuit?
A To store electrical energy
B To control the flow of current
C To amplify the signal
D To convert energy to mechanical form
A resistor limits or controls the flow of electrical current. It converts electrical energy into heat, reducing the current in a circuit according to Ohm’s law.
What is the formula for power in an AC circuit?
A P = V * I
B P = I² * R
C P = V² / R
D P = I * V * cos(θ)
In AC circuits, the power formula is **P = I * V * cos(θ)**, where **I** is the current, **V** is the voltage, and **θ** is the phase angle between the current and voltage. This formula accounts for the power factor.
What happens to the total resistance in a parallel circuit when more resistors are added?
A It increases
B It decreases
C It remains the same
D It becomes zero
In a parallel circuit, the total resistance decreases as more resistors are added. This happens because the total resistance is calculated by the reciprocal of the sum of reciprocals of the individual resistances.
What is the main difference between an ideal voltage source and a practical voltage source?
A An ideal voltage source has zero internal resistance
B A practical voltage source has no resistance
C An ideal voltage source can supply infinite current
D A practical voltage source has infinite internal resistance
An ideal voltage source provides a constant voltage regardless of the current drawn from it, and it has zero internal resistance. A practical voltage source, however, has some internal resistance.
Which of the following describes a combination circuit?
A A circuit with only resistors
B A circuit with only capacitors
C A circuit containing both series and parallel components
D A circuit with only inductors
A combination circuit contains both series and parallel components. Analyzing such circuits requires using the rules for both series and parallel circuits.
What does the term “impedance” refer to in an AC circuit?
A The total opposition to current flow
B The resistance in a DC circuit
C The total power in the circuit
D The voltage drop across a resistor
Impedance (Z) is the total opposition to current flow in an AC circuit, which includes both resistance (R) and reactance (X). It is measured in ohms (Ω).
What does the term “admittance” refer to in an AC circuit?
A The total resistance in the circuit
B The reciprocal of impedance
C The total voltage in the circuit
D The current through the circuit
Admittance (Y) is the reciprocal of impedance (Z) and measures how easily a circuit allows current to flow. It is the inverse of impedance and is measured in siemens (S).
What is the unit of inductance?
A Ohm
B Henry
C Farad
D Tesla
The unit of inductance is the henry (H). It represents the ability of an inductor to oppose changes in current.
What happens at resonance in an RLC circuit?
A The circuit behaves as a pure resistor
B The circuit has maximum impedance
C The impedance is minimized, and current is maximized
D The voltage is minimized
At resonance, the inductive reactance (XL) equals the capacitive reactance (XC), causing them to cancel each other out. This minimizes the total impedance and maximizes the current in the circuit.
What is a feedback mechanism used for in an electrical circuit?
A To enhance the power supply
B To stabilize and control the circuit’s output
C To increase the voltage
D To store electrical energy
Feedback is used to control and stabilize the output of a circuit. Negative feedback, in particular, helps to stabilize amplifiers and other systems by reducing gain fluctuations.
What is the purpose of a transformer in a circuit?
A To convert AC to DC
B To increase or decrease voltage levels
C To regulate the current flow
D To store energy
A transformer changes the voltage level in an AC circuit. It can step up or step down the voltage, depending on the turns ratio between its primary and secondary windings.
What is the primary role of a diode in a circuit?
A To amplify signals
B To convert AC to DC
C To store electrical energy
D To regulate voltage
A diode allows current to flow only in one direction, making it essential for rectification, where it converts alternating current (AC) into direct current (DC).
In an AC circuit, what is a sinusoidal waveform?
A A waveform that contains only DC signals
B A periodic waveform that varies smoothly in sine shape
C A waveform that contains only high-frequency signals
D A non-periodic waveform
A sinusoidal waveform is a smooth, repetitive oscillation that follows a sine function. It is commonly found in AC circuits, where voltage and current vary sinusoidally with time.
What is the formula for total power in a series circuit with a resistive load?
A P = I² * R
B P = V² / R
C P = V * I
D P = I * V * cos(θ)
The total power dissipated in a resistive load in a series circuit is given by **P = I² * R**, where **I** is the current and **R** is the resistance.
What is a digital circuit?
A A circuit that uses continuous signals
B A circuit that uses discrete voltage levels (0 and 1)
C A circuit designed for analog signal processing
D A circuit that stores electrical energy
Digital circuits process signals that are either in a “high” state (1) or a “low” state (0), using discrete voltage levels. They are used in computers, logic gates, and other digital systems.
What is the unit of electric current?
A Volt
B Ampere
C Ohm
D Watt
The unit of electric current is **ampere (A)**. One ampere represents the flow of one coulomb of charge per second.
What is the basic unit of voltage?
A Ohm
B Ampere
C Volt
D Joule
The unit of voltage is **volt (V)**. It is defined as the potential difference that will cause one ampere of current to flow through a resistance of one ohm.
Which of the following describes the behavior of a purely resistive circuit in AC?
A The voltage and current are out of phase by 90 degrees.
B The voltage and current are in phase.
C The current lags the voltage by 90 degrees.
D The voltage and current are unrelated.
In a purely resistive circuit, the **voltage and current are in phase**, meaning they reach their maximum and minimum values at the same time.
What does the term “transient analysis” in electrical circuits refer to?
A The study of a circuit’s behavior in steady-state conditions.
B The study of a circuit’s behavior when a sudden change in conditions occurs.
C The study of the voltage drop across resistors.
D The calculation of power in AC circuits.
**Transient analysis** involves analyzing a circuit’s behavior when it is subject to sudden changes, such as when a switch is turned on or off.
What does the term “steady-state analysis” refer to in electrical circuits?
A The study of short circuits.
B The study of long-term behavior of a circuit.
C The study of behavior during sudden changes.
D The analysis of digital circuits.
**Steady-state analysis** refers to the long-term behavior of a circuit after transient effects have settled, such as when the voltages and currents become constant.
What is a phasor in an AC circuit?
A A time-domain representation of current.
B A vector that represents a sinusoidal function in the frequency domain.
C A representation of voltage as a sinusoidal waveform.
D A capacitor in an AC circuit.
A **phasor** is a complex number that represents a sinusoidal waveform. It is used to simplify the analysis of AC circuits by converting sinusoidal voltages and currents into complex numbers.
What is the resonance condition in an RLC circuit?
A The inductive reactance equals the capacitive reactance.
B The total resistance equals zero.
C The current is minimized.
D The capacitor is fully discharged.
**Resonance** occurs in an RLC circuit when the inductive reactance equals the capacitive reactance. This minimizes the impedance and maximizes the current in the circuit.
Which of the following is true for a series circuit?
A The total current is divided among the components.
B The total resistance is the sum of individual resistances.
C The total voltage is the same across each component.
D The total resistance is always constant.
In a **series circuit**, the total resistance is the sum of the individual resistances. This means that as more resistors are added, the total resistance increases.
What is the total resistance of two resistors, 3 ohms and 6 ohms, connected in parallel?
A 9 ohms
B 2 ohms
C 1.5 ohms
D 4.5 ohms
The total resistance for resistors in parallel is given by:
**1/R_total = 1/R1 + 1/R2**.
So for 3 ohms and 6 ohms,
**1/R_total = 1/3 + 1/6 = 1/2**,
thus **R_total = 2 ohms**.
What happens to the total impedance in a series RLC circuit at resonance?
A The impedance is minimized.
B The impedance is maximized.
C The current is minimized.
D The impedance is constant.
At **resonance** in a series RLC circuit, the inductive reactance cancels out the capacitive reactance, resulting in a **minimum total impedance** and maximum current.
What does the power factor in an AC circuit measure?
A The ratio of voltage to current.
B The total power used by the circuit.
C The ratio of real power to apparent power.
D The voltage drop across the resistor.
The **power factor** is the ratio of **real power** (the power actually used by the circuit) to **apparent power** (the total power supplied to the circuit). It indicates how efficiently the circuit is using power.
What is the primary purpose of an electrical filter in a circuit?
A To amplify signals.
B To remove unwanted frequencies.
C To increase the voltage.
D To store energy.
**Electrical filters** are designed to allow certain frequencies to pass while blocking others. They are commonly used in signal processing, audio systems, and communication circuits.
What is the main role of a transformer in an electrical circuit?
A To convert AC to DC.
B To change the voltage level.
C To regulate the current.
D To store energy.
A **transformer** is used to change the **voltage level** in an AC circuit, either stepping it up (increasing voltage) or stepping it down (decreasing voltage).
What is the unit of inductance?
A Farad
B Ohm
C Henry
D Volt
The unit of inductance is **henry (H)**. It represents the ability of an inductor to resist changes in current and store energy in a magnetic field.
In a DC circuit, what happens if the power factor is 1?
A The circuit is inefficient.
B The circuit uses all the power effectively.
C The circuit has no power loss.
D The current is zero.
A **power factor of 1** means that all the power supplied to the circuit is being used effectively, with no power lost due to phase differences between current and voltage.
What is the purpose of a feedback loop in an amplifier circuit?
A To regulate the voltage.
B To stabilize the output.
C To increase the frequency of operation.
D To store energy.
**Feedback** in an amplifier circuit is used to **stabilize the output** by reducing fluctuations and ensuring a steady and consistent signal.
What is the main function of a diode in a circuit?
A To amplify the signal.
B To allow current to flow in only one direction.
C To store electrical energy.
D To resist the flow of current.
A **diode** is a semiconductor device that allows **current to flow in one direction only**, making it useful for rectification (converting AC to DC).
What happens in a parallel circuit when more resistors are added?
A The total current decreases.
B The total resistance decreases.
C The total resistance increases.
D The total voltage increases.
In a **parallel circuit**, adding more resistors **decreases the total resistance** because the total resistance is the reciprocal of the sum of reciprocals of the individual resistances.
What is the primary purpose of an energy storage component like a capacitor?
A To increase the current.
B To store electrical energy for later use.
C To resist voltage spikes.
D To convert AC to DC.
A **capacitor** stores electrical energy in an electric field and can release this energy when needed. It is commonly used in smoothing and energy storage applications.
What is an equivalent circuit used for?
A To simplify the analysis of a complex circuit.
B To add more power to a circuit.
C To increase the current in a circuit.
D To filter out unwanted frequencies.
An **equivalent circuit** is a simplified version of a complex circuit that uses basic components like resistors, capacitors, and inductors to model the same behavior for easier analysis.