Electrical Systems MCQs
What is the unit of electrical resistance?
A) Volt
B) Ampere
C) Ohm
D) Watt
Answer: C) Ohm
Ohm’s Law relates which three electrical quantities?
A) Voltage, Current, and Power
B) Voltage, Current, and Resistance
C) Current, Power, and Resistance
D) Voltage, Power, and Capacitance
Answer: B) Voltage, Current, and Resistance
What is the unit of electrical power?
A) Volt
B) Ampere
C) Ohm
D) Watt
Answer: D) Watt
In a series circuit, how is the total resistance calculated?
A) Sum of all resistances
B) Product of all resistances
C) Reciprocal of the sum of reciprocals
D) Reciprocal of the product of all resistances
Answer: A) Sum of all resistances
What is the purpose of a transformer?
A) To convert AC to DC
B) To step up or step down voltage
C) To store electrical energy
D) To regulate current flow
Answer: B) To step up or step down voltage
Which of the following devices stores electrical energy in an electric field?
A) Inductor
B) Capacitor
C) Transformer
D) Resistor
Answer: B) Capacitor
What is the unit of capacitance?
A) Farad
B) Henry
C) Ohm
D) Coulomb
Answer: A) Farad
Which component opposes changes in current flow?
A) Resistor
B) Capacitor
C) Inductor
D) Transformer
Answer: C) Inductor
In AC circuits, what does the term “reactance” refer to?
A) Resistance to alternating current
B) Total opposition to current flow
C) Opposition due to capacitance and inductance
D) Measure of power dissipation
Answer: C) Opposition due to capacitance and inductance
The power factor of an AC circuit is defined as:
A) The ratio of real power to apparent power
B) The ratio of reactive power to real power
C) The ratio of apparent power to real power
D) The ratio of voltage to current
Answer: A) The ratio of real power to apparent power
What type of circuit is used to convert alternating current (AC) to direct current (DC)?
A) Rectifier
B) Inverter
C) Transformer
D) Oscillator
Answer: A) Rectifier
In a parallel circuit, how is the total resistance calculated?
A) Sum of all resistances
B) Reciprocal of the sum of reciprocals
C) Product of all resistances
D) Average of all resistances
Answer: B) Reciprocal of the sum of reciprocals
What is the primary function of a diode in an electrical circuit?
A) To allow current flow in both directions
B) To prevent current flow
C) To allow current flow in only one direction
D) To store electrical energy
Answer: C) To allow current flow in only one direction
Which device is used to measure electrical current?
A) Voltmeter
B) Ohmmeter
C) Ammeter
D) Wattmeter
Answer: C) Ammeter
What does the term “short circuit” refer to?
A) A complete path for current with very low resistance
B) A circuit with high resistance
C) A circuit with no current flow
D) A break in the circuit path
Answer: A) A complete path for current with very low resistance
Which of the following components is used to protect circuits from overcurrent?
A) Capacitor
B) Inductor
C) Fuse
D) Diode
Answer: C) Fuse
What is the function of a relay in an electrical circuit?
A) To store energy
B) To amplify signals
C) To switch or control a circuit remotely
D) To convert AC to DC
Answer: C) To switch or control a circuit remotely
What does an oscilloscope measure?
A) Voltage only
B) Current only
C) Voltage as a function of time
D) Resistance
Answer: C) Voltage as a function of time
In a three-phase system, what is the phase difference between any two phases?
A) 60 degrees
B) 90 degrees
C) 120 degrees
D) 180 degrees
Answer: C) 120 degrees
What is the function of a circuit breaker?
A) To increase voltage
B) To protect the circuit from overloads or short circuits
C) To measure current
D) To rectify AC to DC
Answer: B) To protect the circuit from overloads or short circuits
Which type of motor is commonly used for household appliances?
A) Synchronous Motor
B) Induction Motor
C) DC Motor
D) Stepper Motor
Answer: B) Induction Motor
What is the term for the rate at which electrical energy is consumed?
A) Power
B) Voltage
C) Current
D) Resistance
Answer: A) Power
In a series circuit, if one resistor fails, what happens to the rest of the circuit?
A) The current increases
B) The circuit continues to function
C) The entire circuit is broken
D) The voltage decreases
Answer: C) The entire circuit is broken
Which component is used to control the flow of current in a circuit by varying its resistance?
A) Capacitor
B) Inductor
C) Resistor
D) Transformer
Answer: C) Resistor
What is the primary function of a capacitor in an AC circuit?
A) To oppose changes in voltage
B) To oppose changes in current
C) To amplify signals
D) To store energy as magnetic fields
Answer: A) To oppose changes in voltage
What is the typical voltage of a standard household electrical outlet in North America?
A) 120 V
B) 220 V
C) 240 V
D) 12 V
Answer: A) 120 V
What is the purpose of an inverter in an electrical system?
A) To convert DC to AC
B) To convert AC to DC
C) To store electrical energy
D) To step up or step down voltage
Answer: A) To convert DC to AC
In a resistive circuit, if the voltage across a resistor is doubled, what happens to the current?
A) It doubles
B) It remains the same
C) It halves
D) It quadruples
Answer: A) It doubles
Which device converts electrical energy into mechanical energy?
A) Transformer
B) Capacitor
C) Motor
D) Generator
Answer: C) Motor
What is the term for the energy lost in a conductor due to resistance?
A) Power Dissipation
B) Power Factor
C) Reactive Power
D) Apparent Power
Answer: A) Power Dissipation
What is the function of a voltage regulator?
A) To vary the resistance in a circuit
B) To maintain a constant voltage level
C) To convert AC to DC
D) To measure voltage fluctuations
Answer: B) To maintain a constant voltage level
What is the principle behind the operation of a DC motor?
A) Electromagnetic induction
B) The interaction of a magnetic field and current-carrying conductors
C) Capacitive reactance
D) Resistive heating
Answer: B) The interaction of a magnetic field and current-carrying conductors
In an AC circuit, what is the purpose of a capacitor’s reactance?
A) To oppose changes in current
B) To oppose changes in voltage
C) To amplify signals
D) To store electrical energy
Answer: B) To oppose changes in voltage
Which of the following describes the behavior of an ideal voltage source?
A) Provides constant voltage regardless of the current
B) Provides constant current regardless of the voltage
C) Provides variable voltage depending on the load
D) Provides variable current depending on the voltage
Answer: A) Provides constant voltage regardless of the current
What does the term “power factor” measure in an electrical circuit?
A) The ratio of real power to reactive power
B) The ratio of apparent power to real power
C) The ratio of reactive power to real power
D) The ratio of real power to apparent power
Answer: D) The ratio of real power to apparent power
Which component is used to step up or step down voltage levels in AC circuits?
A) Inductor
B) Capacitor
C) Transformer
D) Resistor
Answer: C) Transformer
What does a wattmeter measure?
A) Voltage
B) Current
C) Power
D) Resistance
Answer: C) Power
In an electrical circuit, what does the term “short circuit” mean?
A) A connection with very high resistance
B) A connection with very low resistance
C) A circuit with an open switch
D) A circuit with no current flow
Answer: B) A connection with very low resistance
Which type of circuit is used to generate a constant current?
A) Series Circuit
B) Parallel Circuit
C) Current Source Circuit
D) Voltage Divider Circuit
Answer: C) Current Source Circuit
What is the purpose of an electrical fuse?
A) To prevent circuit overload by breaking the circuit
B) To increase voltage levels
C) To convert AC to DC
D) To measure current
Answer: A) To prevent circuit overload by breaking the circuit
What is the primary difference between AC and DC?
A) AC flows in one direction only, while DC reverses direction periodically
B) DC flows in one direction only, while AC reverses direction periodically
C) AC has constant voltage, while DC has varying voltage
D) DC has constant current, while AC has varying current
Answer: B) DC flows in one direction only, while AC reverses direction periodically
What is the function of an electric generator?
A) To convert mechanical energy into electrical energy
B) To convert electrical energy into mechanical energy
C) To store electrical energy
D) To measure electrical energy
Answer: A) To convert mechanical energy into electrical energy
Which electrical component is used to oppose changes in voltage in a circuit?
A) Inductor
B) Capacitor
C) Resistor
D) Diode
Answer: B) Capacitor
What is the function of an electrical transformer?
A) To convert mechanical energy into electrical energy
B) To convert electrical energy into mechanical energy
C) To change the voltage level in an AC circuit
D) To store electrical energy
Answer: C) To change the voltage level in an AC circuit
What does the term “impedance” refer to in an AC circuit?
A) Resistance to current flow
B) Total opposition to current flow, including resistance and reactance
C) Power dissipation
D) Voltage drop across a resistor
Answer: B) Total opposition to current flow, including resistance and reactance
What is the primary function of a relay?
A) To store electrical energy
B) To switch or control electrical circuits
C) To convert AC to DC
D) To measure electrical parameters
Answer: B) To switch or control electrical circuits
Which type of electrical current is typically used in household appliances?
A) Direct Current (DC)
B) Alternating Current (AC)
C) Pulsating DC
D) Variable Frequency AC
Answer: B) Alternating Current (AC)
What is the purpose of an electrical capacitor in a filter circuit?
A) To block DC signals and allow AC signals to pass
B) To store electrical energy
C) To amplify electrical signals
D) To convert AC signals to DC
Answer: A) To block DC signals and allow AC signals to pass
Which device is used to convert mechanical energy into electrical energy?
A) Battery
B) Generator
C) Transformer
D) Capacitor
Answer: B) Generator
In a parallel circuit with multiple resistors, how does the total current relate to the individual currents?
A) Total current is equal to the sum of individual currents
B) Total current is equal to the product of individual currents
C) Total current is the same as the current through each resistor
D) Total current is equal to the reciprocal of the sum of individual currents
Answer: A) Total current is equal to the sum of individual currents