Electrical Measuring Instruments stb MCQs - Physics 12th - Chapter 15 - Sindh Textbook Board

         

ELECTRICAL MEASURING INSTRUMENTS

        

1. The moving coil galvanometer is based on the principle of:

a) Electromagnetic induction

b) Coulomb's law

c) Ohm's law

d) Newton's laws of motion

2. The sensitivity of a moving coil galvanometer can be increased by:

a) Increasing the number of turns in the coil

b) Decreasing the number of turns in the coil

c) Increasing the resistance in series with the coil

d) Decreasing the resistance in series with the coil

3. An ammeter is connected in:

a) Series

b) Parallel

c) Either series or parallel, depending on the circuit

d) None of the above

4. The resistance of an ideal ammeter is:

a) Zero

b) Very high

c) Very low

d) Variable

5. Which of the following devices is used to measure electric current?

a) Ammeter

b) Voltmeter

c) Wheatstone bridge

d) Ohmmeter

6. A voltmeter is always connected in:

a) Series

b) Parallel

c) Either series or parallel, depending on the circuit

d) None of the above

7. The internal resistance of an ideal voltmeter is:

a) Zero

b) Very high

c) Very low

d) Variable

8. The Wheatstone bridge is used to measure:

a) Voltage

b) Current

c) Resistance

d) Power

9. In a Wheatstone bridge, the balance condition occurs when:

a) The ratio of resistances in the opposite arms is equal

b) The ratio of resistances in the adjacent arms is equal

c) The sum of resistances in one pair of arms is equal to the sum of resistances in the other pair of arms

d) The total resistance of the bridge is zero

10. A meter bridge is based on the principle of:

a) Capacitance

b) Inductance

c) Resistance

d) Mutual inductance

11. The principle of a meter bridge is used to measure:

a) Voltage

b) Current

c) Resistance

d) Power

12. A post office box (P.O. Box) is used to measure:

a) Voltage

b) Current

c) Resistance

d) Power

13. The Ohmmeter is used to measure:

a) Voltage

b) Current

c) Resistance

d) Power

14. The principle of a potentiometer is used to measure:

a) Voltage

b) Current

c) Resistance

d) Power

15. A potentiometer measures potential difference by comparing it with a:

a) Standard cell

b) Galvanometer

c) Voltmeter

d) Ammeter

16. The AVOmeter is a combination of:

a) Ammeter and voltmeter

b) Ammeter and ohmmeter

c) Voltmeter and ohmmeter

d) Voltmeter and wattmeter

17. The AVOmeter can measure:

a) Voltage only

b) Current only

c) Resistance only

d) Voltage, current, and resistance

18. The AVOmeter is connected in a circuit:

a) In series

b) In parallel

c) Either series or parallel, depending on the circuit

d) None of the above

19. Which of the following statements is true regarding the AVOmeter?

a) It has a fixed range of measurement

b) It can measure both AC and DC quantities

c) It is not affected by the polarity of the connections

d) It does not require calibration

20. The principle of a potentiometer is used to measure:

a) Voltage

b) Current

c) Resistance

d) Power

21. The resistance of a wire is 10 Ω. If two identical wires are connected in parallel, what will be the equivalent resistance?

a) 5 Ω

b) 10 Ω

c) 20 Ω

d) 40 Ω

22. A voltmeter has an internal resistance of 100 kΩ. If the voltmeter reads 2 V, what is the potential difference across its terminals?

a) 200 V

b) 20 V

c) 2 mV

d) 20 mV

23. A galvanometer with a full-scale deflection of 5 mA has a shunt resistance of 20 Ω. What is the current passing through the galvanometer if a shunt is connected across it?

a) 1 mA

b) 5 mA

c) 10 mA

d) 25 mA

24. The resistance of a wire is 20 Ω. If three identical wires are connected in series, what will be the equivalent resistance?

a) 60 Ω

b) 40 Ω

c) 20/3 Ω

d) 20/9 Ω

25. The resistance of a wire is 15 Ω. If four identical wires are connected in parallel, what will be the equivalent resistance?

a) 60 Ω

b) 30 Ω

c) 3.75 Ω

d) 2.5 Ω

26. A potentiometer has a total resistance of 200 Ω. If the unknown emf being measured is connected across the potentiometer, and a null point is obtained when the balance length is 80 cm, what is the emf?

a) 40 V

b) 50 V

c) 60 V

d) 80 V

27. In a Wheatstone bridge, the ratio of resistances in the adjacent arms is 2:3. If the resistance in one of the arms is 6 Ω, what is the resistance in the other arm?

a) 4 Ω

b) 9 Ω

c) 12 Ω

d) 18 Ω

28. A meter bridge has a wire of length 100 cm. If the null point is obtained at 30 cm from one end, what is the resistance being measured?

a) 30 Ω

b) 50 Ω

c) 70 Ω

d) 100 Ω

29. The resistance of a wire is 25 Ω. If five identical wires are connected in series, what will be the equivalent resistance?

a) 5 Ω

b) 25 Ω

c) 125 Ω

d) 625 Ω

30. A voltmeter has an internal resistance of 1 MΩ. If the voltmeter reads 10 V, what is the potential difference across its terminals?

a) 10 MV

b) 10 kV

c) 10 V

d) 1 mV

ANSWER KEY:

1. a) Electromagnetic induction
2. a) Increasing the number of turns in the coil
3. a) Series
4. b) Very high
5. a) Ammeter
6. b) Parallel
7. b) Very high
8. c) Resistance
9. a) The ratio of resistances in the opposite arms is equal
10. c) Resistance
11. c) Resistance
12. c) Resistance
13. c) Resistance
14. a) Voltage
15. a) Standard cell
16. a) Ammeter and voltmeter
17. d) Voltage, current, and resistance
18. a) In series
19. b) It can measure both AC and DC quantities
20. a) Voltage
21. a) 5 Ω
22. c) 2 mV
23. c) 10 mA
24. b) 40 
25. c) 3.75 Ω
26. a) 40 V
27. c) 12 Ω
28. b) 50 Ω
29. c) 125 Ω
30. b) 10 kV