Lecture 1: Basics of Electrical Measurements

1. What is the primary purpose of electrical measurements?

a) To increase power consumption
b) To control electrical circuits
c) To ensure accurate readings of electrical quantities
d) To generate electricity
Answer: c

2. Which of the following is NOT a fundamental electrical quantity

measured in electrical systems?
a) Voltage
b) Current
c) Resistance
d) Pressure
Answer: d

3. The accuracy of an instrument refers to:

a) The ability to repeat measurements consistently
b) The closeness of a measured value to the true value
c) The smallest detectable change in a measured quantity
d) The speed of response of an instrument
Answer: b

Lecture 2: Characteristics of Instruments and Measurement

Systems
4. What is the major problem encountered with any measuring
instrument?
a) Sensitivity
b) Error
c) Response time
 d) Size
Answer: b

5. Precision in measurement refers to:

a) The ability of an instrument to provide the same reading for
repeated measurements
b) The difference between measured and true values
c) The smallest change an instrument can detect
d) The ability to measure dynamic changes
Answer: a

6. Which of the following is a desirable static characteristic of an

instrument?
a) Drift
b) Hysteresis
c) Reproducibility
d) Noise
Answer: c

7. Linearity in an instrument means:

a) The output changes non-linearly with input
b) The output is independent of input
c) The output varies proportionally with the input
d) The instrument has a long response time
Answer: c

8. What is the term for the smallest measurable change in an

instrument’s reading?
a) Resolution
b) Accuracy
c) Sensitivity
d) Drift
Answer: a
 9. What type of drift occurs when there is a proportional change along
the entire scale?
a) Zero drift
b) Span drift
c) Zonal drift
d) Response drift
Answer: b

10.Hysteresis in a measuring instrument is caused by:

a) Variations in power supply
b) Mechanical friction and magnetic effects
c) High sensitivity
d) High precision
Answer: b

Dynamic Characteristics of Instruments

11.What does “speed of response” indicate in an instrument?

a) The speed of electricity in a circuit
b) The time it takes for an instrument to register a change in input
c) The number of readings taken per second
d) The frequency of voltage signals
Answer: b

12.The time required for an instrument to settle at a final value is

called:
a) Response time
b) Resolution time
c) Dead zone
d) Threshold time
Answer: a

13.Fidelity in a measurement system refers to:

a) The ability to measure small changes
 b) The accuracy of the final output
c) The ability to reproduce the output in the same form as input
d) The time delay in measurements
Answer: c

14.Dynamic error is defined as:

a) The error due to instrument calibration issues
b) The difference between the true time-varying quantity and the
indicated output
c) The inaccuracy due to external interference
d) The variation in static characteristics
Answer: b

15.What is the significance of the time constant in an instrument?

a) It determines the sensitivity of an instrument
b) It indicates the instrument’s accuracy
c) It defines how fast the instrument reaches 63.2% of its final value
d) It represents the maximum drift of an instrument
Answer: c

Lecture 3: Errors in Measurements & Statistical Analysis

1. Gross errors are primarily caused by:
a) Instrumental defects
b) Human mistakes
c) Environmental fluctuations
d) Random noise
Answer: b

2. Systematic errors can be reduced by:

a) Taking more readings
b) Recalibrating the instrument
c) Averaging measurements
 d) Using a different observer
Answer: b

3. The standard deviation of a dataset measures:

a) The mean value
b) The spread of data points
c) The instrument’s full-scale error
d) The arithmetic average
Answer: b

4. A voltmeter with ±2% accuracy at 100V measures 50V. The limiting

error is:
a) ±1%
b) ±2%
c) ±4%
d) ±0.5%
Answer: c
Limiting error doubles when measuring half-scale: 2V error → (2/50)
× 100 = 4%

5. Random errors can be minimized by:

a) Using expensive instruments
b) Taking multiple readings and averaging
c) Ignoring outliers
d) Calibrating once a year
Answer: b
Averaging reduces random noise

6. The algebraic sum of deviations from the mean is always:

a) Positive
b) Negative
c) Zero
d) Equal to variance
Answer: c
(∑(xᵢ - x̄) = 0)
7. A voltmeter with ±1% accuracy at 300V measures 100V. The limiting
error is:
a) ±1%
b) ±3%
c) ±0.33%
d) ±2%
Answer: b
(3V error → 3/100 × 100 = 3%)

8. Which error is not eliminated by statistical methods?

a) Random
b) Gross
c) Systematic
d) Environmental
Answer: b
Gross errors (human mistakes) require procedural fixes, not math.

9. Parallax error falls under:

a) Observational systematic error
b) Random error
c) Gross error
d) Hysteresis
Answer: a
Caused by incorrect viewing angle of analog instruments.

10.For readings [10.2, 10.4, 10.1, 10.3], the average deviation is:
a) 0.1
b) 0.125
c) 0.075
d) 0.2
Answer: b
Mean=10.25; ∑|d|=0.5; Avg dev=0.5/4=0.125

11.If σ=0.5 for 10 readings, the variance is:

a) 0.25
 b) 0.28
c) 0.5
d) 1.0
Answer: b
For finite data, V=σ²×(n/(n-1))=0.25×(10/9)≈0.28

Lecture 4: Indicating Instruments

1. Moving-iron instruments can measure:
a) DC only
b) AC only
c) Both AC and DC
d) High-frequency signals only
Answer: c

2. The scale of a moving-iron instrument is:

a) Uniform
b) Linear
c) Non-uniform (crowded at the start)
d) Logarithmic
Answer: c
(θ ∝ I²)

3. Damping torque is used to:

a) Increase sensitivity
b) Prevent pointer oscillations
c) Reduce hysteresis
d) Calibrate the instrument
Answer: b

4. A PMMC with mirrored scales prevents:

a) Magnetic interference
b) Parallax error
c) Temperature errors
 d) Overload damage
Answer: b

5. A moving-iron ammeter reads 5A DC. For 5A RMS AC, the pointer

will:
a) Show 5A
b) Show 7.07A
c) Oscillate
d) Read zero
Answer: a
MI instruments respond to RMS values (AC=DC RMS equivalence).

Lecture 5: PMMC Instruments & Range Extension

1. A PMMC ammeter vibrates violently when connected to AC. This
proves:
a) Torque reverses direction
b) Eddy currents failed
c) Shunt is defective
d) Magnetic field collapsed
Answer: a

2. An Ayrton shunt is preferred over ordinary shunts because it:

a) Prevents open-circuit damage
b) Costs less
c) Works for AC
d) Has no multipliers
Answer: a

3. A 50μA, 2kΩ meter needs to measure 5mA. The shunt power

dissipation is:
a) 2.5μW
b) 5μW
c) 10μW
 d) 25μW
Answer: b

4. A 100V voltmeter with 20kΩ/V sensitivity has total resistance:

a) 20kΩ
b) 2MΩ
c) 200kΩ
d) 5kΩ
Answer: b

5. Multiplier resistors use carbon because it has:

a) High inductance
b) Low temp coefficient
c) Negative resistance
d) Color coding
Answer: b

Experimental/Case-Based MCQs
12.A student measures resistance 5 times: [10.1, 10.3, 10.0, 9.8,
10.2]Ω. The true value is 10.0Ω. The measurements show:
a) Random errors only
b) Systematic + random
c) Gross errors
d) Perfect accuracy
Answer: a
Mean=10.08Ω (close to true value) with scatter → random errors
dominate.

13.A PMMC ammeter vibrates violently when connected to AC. This

proves:
a) Torque reverses direction
b) Eddy currents failed
c) Shunt is defective
d) Magnetic field collapsed
Answer: a