What is the effect of temperature on the resistance of a metallic conductor?
A Resistance increases with temperature
B Resistance decreases with temperature
C Resistance remains constant
D Resistance becomes zero
In metallic conductors, the resistance increases with temperature due to increased collisions between electrons and lattice ions.
What is the frequency of AC supply in the USA?
A 50 Hz
B 60 Hz
C 100 Hz
D 25 Hz
The standard frequency of AC supply in the USA is 60 Hz, meaning the current changes direction 60 times per second.
What is the primary cause of energy loss in a transformer?
A Copper loss
B Eddy current loss
C Hysteresis loss
D All of the above
Transformers experience energy loss due to copper loss (in winding resistance), eddy current loss (in the core), and hysteresis loss (due to magnetization).
What is the role of an Earth wire in a circuit?
A To carry the load current
B To protect against electric shock
C To increase voltage
D To measure resistance
An Earth wire provides a safe path for leakage current to flow into the ground, protecting users from electric shocks.
What type of energy is produced in a generator?
A Mechanical energy
B Chemical energy
C Electrical energy
D Thermal energy
A generator converts mechanical energy into electrical energy using electromagnetic induction.
What is the main factor that determines the capacitance of a capacitor?
A Resistance of the circuit
B Distance between plates
C Length of wire
D Frequency of the supply
The capacitance of a capacitor is directly proportional to the plate area and inversely proportional to the distance between the plates.
What happens when a conductor moves through a magnetic field?
A No effect
B Current is induced in the conductor
C Resistance increases
D Magnetic field decreases
When a conductor moves through a magnetic field, electromagnetic induction generates an EMF, which induces current in the conductor.
What is the purpose of insulation on electrical wires?
A To conduct electricity
B To prevent current leakage
C To increase voltage
D To reduce power loss
Insulation around electrical wires prevents accidental contact, leakage of current, and short circuits.
Which type of current flows in one direction only?
A Alternating Current (AC)
B Direct Current (DC)
C Pulsating Current
D Static Current
Direct Current (DC) flows steadily in one direction, making it suitable for batteries and electronic devices.
Which of the following devices is used to measure electric current?
A Ammeter
B Voltmeter
C Ohmmeter
D Thermometer
An ammeter measures electric current and is connected in series with the circuit to ensure accurate current measurement.
What is the relationship between voltage and current in a purely capacitive circuit?
A Voltage leads current by 90°
B Voltage and current are in phase
C Current leads voltage by 90°
D Voltage lags current by 180°
In a purely capacitive circuit, the current leads the voltage by 90° because the capacitor charges and discharges during the AC cycle.
Which type of load consumes both active and reactive power?
A Resistive load
B Inductive load
C Capacitive load
D Complex load
A complex load consists of resistive, inductive, and/or capacitive components, consuming both active power (real work) and reactive power (energy storage).
What is the SI unit of conductance?
A Ohm
B Siemens
C Volt
D Ampere
Conductance is measured in siemens (S) and represents the reciprocal of resistance, indicating how easily current flows through a material.
Which component is responsible for energy loss due to eddy currents in a transformer?
A Core
B Windings
C Insulation
D Load
Eddy current losses occur in the transformer core due to the formation of circulating currents induced by the alternating magnetic field.
What is the function of a choke in a fluorescent tube circuit?
A To increase voltage
B To regulate current
C To decrease resistance
D To convert AC to DC
A choke is an inductor that limits the current in a fluorescent tube circuit, preventing excessive current flow.
What is the effect of increasing the cross-sectional area of a conductor on its resistance?
A Resistance increases
B Resistance decreases
C Resistance remains constant
D Resistance becomes infinite
Resistance (\( R \)) is inversely proportional to the cross-sectional area (\( A \)): \( R = \rho \frac{L}{A} \). Increasing \( A \) reduces resistance.
What does a three-phase system provide compared to a single-phase system?
A Higher voltage only
B More efficiency and smoother power delivery
C Less complexity in wiring
D Reduced frequency
A three-phase system delivers power more efficiently and provides a constant torque, which is beneficial for industrial applications.
Which instrument is used to detect faults in electrical wiring?
A Voltmeter
B Multimeter
C Megger
D Galvanometer
A megger is used to measure insulation resistance and detect faults in electrical wiring, ensuring safety and reliability.
What is the primary purpose of a dielectric in a capacitor?
A To reduce current
B To store charge
C To prevent leakage of charge
D To step up voltage
A dielectric is an insulating material placed between the plates of a capacitor to increase its capacitance and prevent charge leakage.
In an AC circuit, what is the phase difference between voltage and current in a purely resistive load?
A 0°
B 90°
C 180°
D 270°
In a purely resistive load, voltage and current are in phase, meaning there is no phase difference between them.
What is the main advantage of using an isolation transformer?
A Reduces voltage
B Increases current
C Provides electrical isolation
D Enhances power factor
An isolation transformer isolates the primary and secondary circuits, ensuring safety by preventing direct electrical contact.
What is the purpose of a lightning arrester in an electrical system?
A To store energy
B To protect equipment from lightning strikes
C To step up voltage
D To reduce resistance
A lightning arrester diverts high-voltage surges caused by lightning to the ground, protecting electrical systems and equipment.
What is the power factor of a purely resistive circuit?
A 0
B 1
C -1
D 0.5
In a purely resistive circuit, the power factor is 1 because voltage and current are in phase, resulting in maximum real power transfer.
What is the role of a thermostat in electrical appliances?
A To measure voltage
B To regulate temperature
C To increase current
D To reduce resistance
A thermostat automatically maintains a set temperature by controlling the power supply to heating or cooling devices.
Which of the following is an application of electromagnetism?
A Electric motor
B Transformer
C Magnetic levitation
D All of the above
Electromagnetism is used in electric motors, transformers, and magnetic levitation systems, demonstrating its versatility in various technologies.
What type of wiring system is commonly used in modern residential buildings?
A Cleat wiring
B Conduit wiring
C Wooden casing wiring
D Lead sheathed wiring
Conduit wiring is commonly used in residential buildings due to its safety, durability, and neat appearance.
What is the effect of increasing frequency on capacitive reactance?
A It increases
B It decreases
C It remains constant
D It becomes infinite
Capacitive reactance (\( X_C = \frac{1}{2 \pi f C} \)) is inversely proportional to frequency (\( f \)), so increasing \( f \) reduces \( X_C \).
What is the unit of magnetic flux density?
A Weber
B Tesla
C Ampere-turn
D Henry
Magnetic flux density is measured in teslas (T), which represent the strength of a magnetic field over a given area.
What is the main characteristic of an ideal voltage source?
A Infinite internal resistance
B Zero internal resistance
C Constant power output
D Variable voltage output
An ideal voltage source has zero internal resistance, providing a constant voltage regardless of the current drawn.
Which device is used to measure the power consumed in a circuit?
A Ammeter
B Wattmeter
C Voltmeter
D Ohmmeter
A wattmeter measures the power consumed in a circuit by determining the product of voltage, current, and the power factor.
What is the relationship between power, voltage, and current in a DC circuit?
A \( P = V/I \)
B \( P = VI \)
C \( P = I^2V \)
D \( P = V^2I \)
In a DC circuit, power (\( P \)) is the product of voltage (\( V \)) and current (\( I \)). This is the fundamental formula for electrical power.
What happens to the total capacitance when capacitors are connected in parallel?
A It increases
B It decreases
C It remains constant
D It becomes zero
The total capacitance in a parallel connection is the sum of individual capacitances: \( C_{\text{total}} = C_1 + C_2 + \dots \).
What is the primary advantage of an AC system over a DC system for power transmission?
A Lower voltage
B Easier to convert voltages using transformers
C No energy loss
D Constant current flow
AC systems allow easy voltage transformation using transformers, reducing transmission losses over long distances.
Which of the following is a non-ohmic device?
A Copper wire
B Resistor
C Filament bulb
D Aluminum wire
The filament bulb is non-ohmic because its resistance changes with temperature, causing a nonlinear relationship between voltage and current.
What is the unit of electric charge?
A Joule
B Ampere
C Coulomb
D Watt
Electric charge is measured in coulombs (C), where 1 coulomb equals the charge transported by a current of 1 ampere in 1 second.
What is the effect of temperature on the resistance of a semiconductor?
A Resistance increases with temperature
B Resistance decreases with temperature
C Resistance remains constant
D Resistance becomes infinite
In semiconductors, increasing temperature provides more energy for charge carriers, reducing resistance.
Which device is used to measure the frequency of an AC signal?
A Voltmeter
B Ammeter
C Oscilloscope
D Ohmmeter
An oscilloscope can measure the frequency of an AC signal by analyzing the waveform displayed on its screen.
What type of loss occurs in a transformer due to the repeated magnetization and demagnetization of the core?
A Copper loss
B Eddy current loss
C Hysteresis loss
D Dielectric loss
Hysteresis loss occurs in the transformer core due to repeated cycles of magnetization and demagnetization, which consume energy.
What is the role of a load in an electrical circuit?
A To store energy
B To consume power
C To increase current
D To generate voltage
A load, such as a light bulb or motor, consumes electrical power to perform work or produce heat, light, or motion.
What is the relationship between magnetic flux density (\( B \)) and magnetic field strength (\( H \)) in a material?
A \( B = H/I \)
B \( B = \mu H \)
C \( B = H \times \mu_0 \)
D \( B = I \times H \)
Magnetic flux density (\( B \)) is the product of magnetic field strength (\( H \)) and the material’s permeability (\( \mu \)).
Which device is used to test the polarity of a DC circuit?
A Ammeter
B Test lamp
C Multimeter
D Voltmeter
A multimeter can measure voltage and indicate the polarity of a DC circuit by showing the direction of current flow.
What is the primary purpose of grounding in electrical systems?
A To increase voltage
B To protect devices from surges and shocks
C To amplify current
D To reduce resistance
Grounding provides a safe path for fault currents to flow into the Earth, preventing damage to devices and reducing the risk of electric shocks.
What is the typical range of power factor in industrial applications?
A 0.1 to 0.5
B 0.5 to 1.0
C -1.0 to 0
D 0 to 0.2
Industrial systems typically operate within a power factor range of 0.5 to 1.0, with higher values indicating more efficient power usage.
Which type of transformer winding is connected to the load?
A Primary winding
B Secondary winding
C Tertiary winding
D Core winding
The secondary winding of a transformer is connected to the load and delivers the output voltage.
What is the effect of increasing the number of turns in a solenoid?
A Decreases magnetic field strength
B Increases magnetic field strength
C Reduces current
D Increases resistance
Increasing the number of turns in a solenoid enhances the magnetic field strength, as \( B \propto N \), where \( N \) is the number of turns.
What is the frequency of AC supply in India?
A 50 Hz
B 60 Hz
C 100 Hz
D 25 Hz
The standard frequency of AC supply in India is 50 Hz, meaning the current completes 50 cycles per second.
What is the purpose of a relay in electrical circuits?
A To measure current
B To amplify voltage
C To control a circuit remotely
D To reduce resistance
A relay uses a small electrical signal to control the operation of a larger electrical circuit, providing isolation and remote switching.
What is the SI unit of inductance?
A Henry
B Weber
C Tesla
D Joule
Inductance is measured in henries (H), where one henry is the inductance that produces one volt when the current changes at one ampere per second.
Which property of a conductor determines its ability to resist current flow?
A Conductivity
B Permeability
C Resistivity
D Dielectric strength
Resistivity (\( \rho \)) is a material property that determines how strongly it resists current flow. It depends on the material’s composition.
What is the primary function of a rheostat?
A To increase resistance
B To adjust current flow
C To reduce voltage
D To step down power
A rheostat is a variable resistor that controls the current flow in a circuit by changing its resistance.