What is the purpose of a load resistor in an electrical circuit?
A To decrease current flow
B To dissipate energy as heat
C To increase voltage
D To store energy
A load resistor converts electrical energy into heat, simulating the load on the circuit and ensuring proper operation during testing or normal use.
Which of the following is a correct formula for electric energy?
A E = P × t
B E = P / t
C E = I² × R
D E = V × R
Electric energy (E) is the product of power (P) and time (t), typically measured in watt-hours or joules.
What is the primary function of a transformer in an electrical circuit?
A To convert AC to DC
B To step up or step down voltage
C To increase current
D To store electrical energy
Transformers are used to adjust voltage levels efficiently through electromagnetic induction, crucial in power distribution systems.
What is the typical voltage of a standard AA battery?
A 1.5 V
B 3 V
C 5 V
D 9 V
Standard AA batteries provide a voltage of 1.5 V, commonly used in small electronic devices.
In which type of circuit does the current divide among multiple paths?
A Series circuit
B Parallel circuit
C Open circuit
D Short circuit
In a parallel circuit, the current splits across different branches, each carrying a portion of the total current.
What is the principle of operation for a DC generator?
A Electrostatic induction
B Electromagnetic induction
C Thermal effect of current
D Magnetic resonance
A DC generator works on electromagnetic induction, producing DC electricity by rotating a coil in a magnetic field.
What is the unit of electric field strength?
A Volt per meter
B Tesla
C Coulomb
D Ampere per meter
Electric field strength is measured in volts per meter (V/m), representing the force experienced by a charge in an electric field.
Which device is used to store electrical energy temporarily?
A Inductor
B Capacitor
C Transformer
D Resistor
A capacitor temporarily stores electrical energy in the form of an electric field between its plates.
What happens to the brightness of a bulb if the voltage across it is doubled?
A Brightness remains the same
B Brightness is halved
C Brightness increases
D Bulb burns out
The brightness of a bulb depends on power, which is proportional to the square of the voltage (P = V² / R). Doubling the voltage significantly increases power and brightness.
Which type of motor is commonly used in household fans?
A Stepper motor
B Synchronous motor
C Induction motor
D DC motor
Single-phase induction motors are commonly used in household fans due to their simplicity and efficiency.
What is the primary purpose of a fuse in a circuit?
A To increase voltage
B To prevent excessive current flow
C To measure resistance
D To amplify current
A fuse breaks the circuit by melting when the current exceeds a safe level, protecting the wiring and devices from damage.
Which law states that the induced EMF in a conductor is proportional to the rate of change of magnetic flux?
A Ohm’s Law
B Kirchhoff’s Voltage Law
C Faraday’s Law
D Lenz’s Law
Faraday’s Law of Electromagnetic Induction states that the induced EMF in a circuit is proportional to the rate of change of magnetic flux linkage.
What is the purpose of insulation in an electrical system?
A To conduct electricity
B To prevent leakage of current
C To increase resistance
D To amplify voltage
Insulation materials prevent accidental contact and leakage of current, ensuring safety and reliability in electrical systems.
What is the primary characteristic of an ideal current source?
A Infinite voltage
B Constant current regardless of load resistance
C Variable current
D High internal resistance
An ideal current source maintains a constant current flow irrespective of the load resistance connected to it.
Which material is commonly used as the core of a transformer?
A Aluminum
B Copper
C Soft iron
D Plastic
Soft iron is used as the core material in transformers due to its high magnetic permeability and low hysteresis loss.
What type of circuit offers only one path for current flow?
A Series circuit
B Parallel circuit
C Open circuit
D Short circuit
In a series circuit, components are connected end-to-end, providing only one path for the current to flow.
Which component is used to measure electrical resistance?
A Ammeter
B Ohmmeter
C Voltmeter
D Thermometer
An ohmmeter measures electrical resistance and is often integrated into multimeters for ease of use.
What is the relationship between power and resistance in a DC circuit?
A P = I²R
B P = V²R
C P = IR²
D P = I/R
In a DC circuit, power (P) is proportional to the square of the current (I) and the resistance (R).
Which instrument is used to measure the insulation resistance of a cable?
A Megger
B Ammeter
C Voltmeter
D Multimeter
A megger measures high resistance, typically used to test the insulation quality of electrical cables.
What is the primary factor affecting the capacitance of a parallel plate capacitor?
A Length of the plates
B Area of the plates and distance between them
C Material of the wires
D Frequency of the current
The capacitance of a parallel plate capacitor is directly proportional to the plate area and inversely proportional to the distance between the plates.
What is the primary function of a voltmeter?
A Measure resistance
B Measure voltage
C Measure current
D Measure power
A voltmeter is used to measure the electrical potential difference (voltage) between two points in a circuit.
How is a voltmeter connected in a circuit?
A In series
B In parallel
C In series-parallel
D Either series or parallel
Voltmeters are connected in parallel across the component to measure the voltage without affecting the circuit.
What does an ammeter measure?
A Voltage
B Resistance
C Current
D Power
An ammeter measures the electric current flowing through a circuit.
How is an ammeter connected in a circuit?
A In parallel
B In series
C In series-parallel
D It depends on the circuit
Ammeters are connected in series to ensure all the current in the circuit flows through the meter for measurement.
What is the main advantage of a multimeter?
A Measures only current
B Measures multiple electrical quantities
C Measures only voltage
D Measures power only
A multimeter can measure voltage, current, and resistance, making it a versatile instrument.
What type of power does a wattmeter measure?
A Apparent power
B Reactive power
C Active power
D Total power
Wattmeters measure the active (real) power consumed by a load in an electrical circuit.
What does an energy meter measure?
A Instantaneous voltage
B Total electrical energy consumed
C Power factor
D Current flow
Energy meters record the total electrical energy used over time, typically in kilowatt-hours (kWh).
Which principle is used in a galvanometer?
A Magnetic induction
B Thermal expansion
C Electromagnetic deflection
D Electrostatic attraction
Galvanometers operate on the principle of electromagnetic deflection, where current passing through a coil creates a magnetic field that interacts with an external magnetic field.
What is the sensitivity of a galvanometer expressed in?
A Amperes
B Ohms
C Microamperes per division
D Volts
The sensitivity of a galvanometer is defined as the smallest current required to produce a detectable deflection.
What does a frequency meter measure?
A Current
B Voltage
C Frequency of an AC signal
D Resistance
Frequency meters measure the number of cycles per second (Hertz) of an alternating current (AC) signal.
What is the function of a phase meter?
A Measure power
B Measure current
C Measure phase difference
D Measure resistance
Phase meters measure the angular difference in phase between two alternating signals.
What is the main purpose of a current transformer?
A To step up voltage
B To step down current for measurement
C To step up current
D To measure resistance
Current transformers reduce high current levels to lower, safer levels suitable for measurement and protection.
How is a current transformer connected in a circuit?
A In series with the load
B In parallel with the load
C Across the voltage supply
D In series-parallel
Current transformers are connected in series with the load so they can measure the entire load current.
What does a potential transformer measure?
A Current
B Resistance
C Voltage
D Power
Potential transformers step down high voltage levels to measurable values for instruments and meters.
Where are potential transformers typically used?
A Low voltage systems
B Medium and high voltage systems
C Battery systems
D DC circuits
Potential transformers are commonly used in medium and high voltage systems to safely measure and monitor voltage.
What is the typical application of a moving iron instrument?
A Measuring resistance
B Measuring AC and DC current
C Measuring frequency
D Measuring capacitance
Moving iron instruments are versatile and used for measuring both AC and DC currents.
Which type of energy meter is used in households?
A Analog energy meter
B Digital energy meter
C Wattmeter
D Multimeter
Digital energy meters are widely used in households for accurate measurement and billing of electrical energy consumption.
What is the purpose of damping in measuring instruments?
A To increase sensitivity
B To stabilize the pointer and reduce oscillations
C To amplify the signal
D To protect the instrument
Damping reduces oscillations in the pointer, allowing it to settle quickly for an accurate reading.
What does the scale of a voltmeter indicate?
A Resistance in ohms
B Voltage in volts
C Power in watts
D Current in amperes
The scale of a voltmeter is calibrated to display the voltage across two points in volts.
What is the typical range of a laboratory-grade ammeter?
A Milliamperes to amperes
B Volts to kilovolts
C Ohms to megaohms
D Watts to kilowatts
Laboratory-grade ammeters are designed to measure currents ranging from milliamperes (mA) to amperes (A).
What is the resistance of an ideal voltmeter?
A Zero
B Infinite
C Very low
D Medium
An ideal voltmeter has infinite resistance to ensure that it does not draw any current from the circuit, thereby not affecting the circuit operation.
What is the resistance of an ideal ammeter?
A Zero
B Infinite
C Very high
D Medium
An ideal ammeter has zero resistance to ensure it does not introduce any voltage drop in the circuit it is measuring.
What type of meter is used to measure both AC and DC voltages?
A Galvanometer
B Multimeter
C Wattmeter
D Energy meter
A multimeter can measure AC and DC voltages, as well as current and resistance, making it versatile.
Which of the following instruments uses a permanent magnet?
A Moving coil voltmeter
B Moving iron ammeter
C Phase meter
D Energy meter
Moving coil instruments use a permanent magnet and are primarily used to measure DC quantities.
What is the deflection torque in a galvanometer proportional to?
A Current through the coil
B Voltage across the terminals
C Resistance of the coil
D Capacitance of the circuit
The deflection torque in a galvanometer is directly proportional to the current passing through its coil.
Which meter can measure electrical energy consumption in a house?
A Wattmeter
B Energy meter
C Multimeter
D Frequency meter
Energy meters measure the total electrical energy consumption over time, commonly used for billing.
What is the typical unit of measurement for an energy meter?
A Kilowatt-hour (kWh)
B Joules (J)
C Watts (W)
D Amperes (A)
Energy meters record energy consumption in kilowatt-hours, where 1 kWh represents the energy used by a 1-kilowatt device running for one hour.
What type of meter is used to measure the frequency of an AC signal?
A Oscilloscope
B Frequency meter
C Multimeter
D Energy meter
Frequency meters measure the number of cycles per second of an alternating current (AC) signal, expressed in Hertz (Hz).
Which principle is used in current transformers?
A Electromagnetic induction
B Thermal expansion
C Electrostatic force
D Magnetic deflection
Current transformers operate on the principle of electromagnetic induction, stepping down current for safe measurement.
Which of the following describes precision in measurement?
A Closeness of a measured value to the true value
B Reproducibility of measurement
C The difference between measured and true value
D Accuracy of the instrument
Precision refers to the consistency of repeated measurements, regardless of how close they are to the actual value.