A moving coil galvanometer has an internal resistance of 10 Ω and a full-scale deflection current of 5 mA. What shunt resistance is required to convert it into an ammeter with a range of 0-5 A?
Which of the following is NOT a source of error in analog voltmeters?
Answer: C
Analog voltmeters are primarily DC devices. Frequency changes affect AC measurements but not the instrument's basic construction errors.
Q.23Hard
In a Kelvin's double bridge used for measuring low resistances (< 0.1 Ω), which configuration is adopted?
Answer: B
Kelvin's double bridge uses cross-connection to eliminate lead resistance errors when measuring very low resistances in industrial applications.
Q.24Easy
A thermocouple generates 50 μV for a temperature difference of 1°C between its junctions. What is its sensitivity?
Answer: A
Sensitivity is the ratio of output to input. Here, sensitivity = 50 μV/1°C = 50 μV/°C.
Q.25Medium
A wattmeter with voltage coil rating of 300 V and current coil rating of 5 A is used to measure power in a circuit. If the actual voltage is 250 V and current is 4 A at power factor 0.8, what will be the wattmeter reading if it has full-scale deflection of 1500 W?
Answer: A
Power = V × I × cos(φ) = 250 × 4 × 0.8 = 800 W. The wattmeter reading equals actual power consumed.
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Q.26Easy
In a CRO probe with 10:1 attenuation ratio, if the actual voltage is 100 V, what voltage appears across the CRO input terminals?
Answer: A
With 10:1 attenuation, the voltage at CRO terminals = Actual voltage/10 = 10100 = 10 V.
Q.27Medium
Which method is most suitable for measuring frequency in the range of 10 Hz to 100 kHz with high accuracy in 2024-25 standards?
Answer: B
Digital frequency counters provide accuracy of ±1 count with real-time display and are industry standard for this frequency range.
Q.28Medium
An AC bridge circuit is used to measure unknown capacitance. At balance, the product of opposite arms satisfies which condition?
Answer: C
For AC bridges at balance condition: Z₁ × Z₄ = Z₂ × Z₃, where Z represents impedance of arms.
Q.29Easy
What is the primary advantage of a digital multimeter over an analog multimeter in industrial measurements?
Answer: B
Digital multimeters eliminate parallax error, provide direct digital readings, and are more user-friendly for industrial applications.
Q.30Medium
In a megohmmeter, what voltage is typically applied across the test terminals to measure very high resistances (> 1 MΩ)?
Answer: A
Megohmmeters use high DC voltages (1-5 kV) to force sufficient current through high resistances for measurable deflection.
Q.31Hard
A strain gauge has gauge factor of 2.1 and resistance change of 5 Ω for a strain of 0.001. What is the original resistance of the gauge?
In a three-phase power measurement using two-wattmeter method, the power factor can be determined from which relationship?
Answer: A
For two-wattmeter method in three-phase systems: tan(φ) = √3(W₁ - W₂)/(W₁ + W₂), used to calculate power factor.
Q.33Medium
A standard cell has an EMF of 1.0186 V at 20°C with temperature coefficient of -0.0004 V/°C. What will be its EMF at 25°C?
Answer: B
EMF at 25°C = 1.0186 - 0.0004 × (25-20) = 1.0186 - 0.002 = 1.0166 ≈ 1.0170 V.
Q.34Easy
Which bridge circuit is specifically designed to measure inductance with small resistance?
Answer: A
Maxwell bridge is used for measuring inductance (especially with small resistance) in industrial and laboratory applications.
Q.35Medium
In a LVDT (Linear Variable Differential Transformer), when the core is at null position, what happens to the output voltage?
Answer: B
At null position in LVDT, the core is centered, and secondary voltages from both coils cancel out, resulting in zero or minimum output.
Q.36Easy
A pressure transducer has sensitivity of 0.5 V/bar. If input pressure varies from 0-10 bar, what is the output voltage range?
Answer: B
Output voltage = Sensitivity × Pressure = 0.5 × 10 = 5 V for maximum pressure of 10 bar.
Q.37Medium
In a potentiometer method for EMF comparison, if standard cell EMF is 1.018 V with 106.4 cm length, and unknown cell requires 107.8 cm, what is unknown EMF?
A light intensity meter using a photocell shows reading of 500 lux. If the luminous intensity of the source is constant, what happens to the reading when distance is doubled?
Answer: B
Illuminance follows inverse square law: E ∝ 1/d²; when distance doubles, illuminance becomes 41th: 4500 = 125 lux.
