Voltmeter Practice Questions
20 free Voltmeter practice questions for the General Science. Tap an option to answer — you get instant feedback, the correct answer, and a detailed explanation for every question.
What is the primary function of a voltmeter in an electrical circuit?
- A To measure the rate at which electrons flow past a point
- B To measure the potential difference between two points
- C To measure the total resistance of the circuit
- D To regulate the current flowing through a load
Correct answer: To measure the potential difference between two points
A voltmeter is designed to measure electrical potential difference, also known as voltage. It determines the difference in electric potential energy per unit charge between two specific points in a circuit.
How should a voltmeter be connected relative to the component whose voltage is being measured?
- A In series with the component
- B In parallel with the component
- C Directly to the negative terminal only
- D Between the power source and the switch
Correct answer: In parallel with the component
To measure the potential difference across a component, the voltmeter must be connected in parallel. This allows it to experience the same voltage drop as the component without significantly altering the current in the main circuit.
An ideal voltmeter is theorized to have which of the following characteristics?
- A Zero resistance
- B Infinite resistance
- C Variable resistance based on current
- D Resistance equal to the circuit load
Correct answer: Infinite resistance
An ideal voltmeter has infinite resistance so that it draws no current from the circuit. If it drew current, it would change the very voltage it is trying to measure, leading to an inaccurate reading.
What happens if a voltmeter is mistakenly connected in series with a circuit load?
- A The circuit current will increase drastically.
- B The voltmeter will likely blow a fuse.
- C The circuit current will drop to nearly zero.
- D The component will operate at double its rated power.
Correct answer: The circuit current will drop to nearly zero.
Because a voltmeter has very high internal resistance, connecting it in series adds that high resistance to the entire circuit. According to Ohm's Law, this causes the total current to drop to a negligible level, effectively 'breaking' the circuit's functionality.
Which basic instrument is converted into a DC voltmeter by connecting a high-resistance multiplier in series?
- A Ammeter
- B Galvanometer
- C Ohmmeter
- D Wheatstone bridge
Correct answer: Galvanometer
A standard moving-coil galvanometer can be converted into a voltmeter by connecting a high-resistance resistor (called a multiplier) in series with it. This limits the current through the sensitive galvanometer while allowing it to measure large potential differences.
The sensitivity of a voltmeter is typically expressed in which units?
- A Volts per Ampere
- B Watts per Ohm
- C Amperes per Volt
- D Ohms per Volt
Correct answer: Ohms per Volt
Voltmeter sensitivity is measured in Ohms per Volt (Ω/V). It represents the total internal resistance of the meter divided by its full-scale voltage reading; a higher value indicates a better meter that draws less current.
In a multi-range voltmeter, different voltage ranges are achieved by using different values of:
- A Parallel shunt resistors
- B Electrolytic capacitors
- C Precision current transformers
- D Series multiplier resistors
Correct answer: Series multiplier resistors
To change the range, different 'multiplier' resistors are switched into series with the meter movement. Higher resistance multipliers are used for higher voltage ranges to keep the current through the meter within safe limits.
What is the main advantage of a Digital Voltmeter (DVM) over an analog voltmeter?
- A It does not require a power source.
- B It has lower internal resistance.
- C It uses a moving needle, which some users find easier to read.
- D It provides higher accuracy and eliminates parallax errors.
Correct answer: It provides higher accuracy and eliminates parallax errors.
Digital voltmeters provide a direct numerical readout, which removes the subjectivity of reading a scale (parallax error). They also generally offer much higher input impedance and greater precision than traditional needle-based analog meters.
Which type of voltmeter is specifically designed to measure the RMS value of alternating current (AC) voltages?
- A Moving coil voltmeter
- B Rectifier voltmeter
- C Peak-reading voltmeter
- D Moving Iron voltmeter
Correct answer: Moving Iron voltmeter
Moving Iron (MI) voltmeters are suitable for both AC and DC measurements. Because the deflection is proportional to the square of the current, they naturally provide a reading corresponding to the Root Mean Square (RMS) value of an AC signal.
A voltmeter reads 12V when connected across a battery. If the same voltmeter is used to measure a 12V source with much higher internal resistance, the reading might drop. This effect is known as:
- A Hysteresis
- B The Doppler effect
- C Electromagnetic interference
- D Loading effect
Correct answer: Loading effect
The loading effect occurs when the voltmeter's own resistance is not high enough compared to the circuit's resistance. The meter acts as a parallel load, drawing enough current to significantly lower the voltage it is intending to measure.
What is the SI unit of measurement indicated on the display of a voltmeter?
- A Watt (W)
- B Joule (J)
- C Coulomb (C)
- D Volt (V)
Correct answer: Volt (V)
The Volt is the SI unit for electric potential. It is defined as one Joule of energy per Coulomb of charge (1 V = 1 J/C).
Which component in an electronic voltmeter (like a vacuum tube voltmeter or FET-input meter) allows for exceptionally high input impedance?
- A An amplifier stage
- B A moving coil
- C A low-value shunt resistor
- D A step-down transformer
Correct answer: An amplifier stage
By using an active amplifier stage (using transistors or vacuum tubes) at the input, the voltmeter can sense voltage while drawing almost no current. This results in input impedances often exceeding 10 million Ohms.
When using an analog voltmeter, from what position should you view the needle to ensure the most accurate reading?
- A Directly from above the needle
- B At a 45-degree angle from the left
- C From the right of the scale
- D From directly beneath the meter face
Correct answer: Directly from above the needle
Viewing the needle from the side creates a 'parallax error' where the needle appears to align with a different mark on the scale. Looking directly from above ensures your line of sight is perpendicular to the scale.
If a voltmeter is designed for DC (Direct Current), what will usually happen if it is connected to an AC (Alternating Current) source?
- A The needle will oscillate rapidly or stay at zero.
- B The meter will show the RMS value accurately.
- C The needle will point to the peak voltage only.
- D The meter will automatically convert the signal to DC.
Correct answer: The needle will oscillate rapidly or stay at zero.
A standard DC meter (PMMC) reacts to the average value of the signal. Since the average value of a symmetrical AC sine wave is zero, the needle will either stay at zero or vibrate slightly if the frequency is very low.
Which of the following describes the 'Full-Scale Deflection' (FSD) of a voltmeter?
- A The maximum voltage measurable on the selected range
- B The minimum voltage the meter can detect
- C The speed at which the needle returns to the zero mark
- D The resistance of the meter at zero volts
Correct answer: The maximum voltage measurable on the selected range
Full-Scale Deflection refers to the point where the needle reaches the highest mark on the scale. Exceeding this value can bury the needle against the stop pin and potentially damage the internal mechanism.
Which instrument combines the functions of a voltmeter, ammeter, and ohmmeter into a single device?
- A Potentiometer
- B Multimeter
- C Wattmeter
- D Oscilloscope
Correct answer: Multimeter
A multimeter (or VOM - Volt-Ohm-Milliammeter) is a versatile tool used by technicians to measure multiple electrical properties by switching between internal circuits and ranges.
To measure a very high voltage (e.g., 10,000V) with a standard voltmeter, which accessory is typically required?
- A A low-resistance shunt wired across the meter terminals
- B A high-voltage probe with a large series resistance
- C A step-down transformer feeding the meter input
- D A capacitor bank connected in series
Correct answer: A high-voltage probe with a large series resistance
A high-voltage probe contains a massive series resistor that drops most of the voltage before it reaches the meter. This protects the user and the instrument while allowing for a scaled-down measurement.
What is the primary difference between a voltmeter and a potentiometer?
- A A voltmeter is more accurate than a potentiometer.
- B A voltmeter measures potential while a potentiometer measures current.
- C A potentiometer draws no current from the source at its null point.
- D A voltmeter can only measure AC while a potentiometer only measures DC.
Correct answer: A potentiometer draws no current from the source at its null point.
A potentiometer is a 'null-balance' instrument. At the point of balance (null), it draws zero current from the source being measured, making it inherently more accurate than a standard voltmeter for precise laboratory work.
Which property of a voltmeter determines its 'resolution'?
- A The maximum voltage it can handle without damage
- B The smallest voltage change it can detect and display
- C The weight and size of the instrument casing
- D The overall length of the attached test leads and probes
Correct answer: The smallest voltage change it can detect and display
Resolution refers to the smallest increment of voltage the meter can distinguish. On a digital voltmeter, this is usually determined by the number of digits (or 'counts') on the display.
Which type of voltmeter uses the force of attraction between two charged plates to move a pointer?
- A Permanent magnet moving coil voltmeter
- B Hot-wire voltmeter
- C Electrostatic voltmeter
- D Induction voltmeter
Correct answer: Electrostatic voltmeter
Electrostatic voltmeters work on the principle of the electrostatic force between charged surfaces. Because they rely on electric fields rather than magnetic fields, they have extremely high input resistance and are used for measuring high voltages.