1. A digital signal has:
(A) Discrete levels of voltage
(B) Continuous voltage
(C) Random noise
(D) Sinusoidal waveform
2. The main advantage of digital electronics over analog is:
(A) High voltage only
(B) Noise immunity and accuracy
(C) High current only
(D) Low frequency
3. A logic “1” in digital circuits represents:
(A) High voltage level
(B) Low voltage level
(C) Zero voltage
(D) Negative voltage
4. The binary number system uses:
(A) 0 and 1
(B) 0, 1, 2
(C) 0,1,2,3
(D) 1–10
5. The decimal equivalent of binary 1011 is:
(A) 13
(B) 12
(C) 10
(D) 11
6. A NOT gate is also called:
(A) Inverter
(B) AND gate
(C) OR gate
(D) NAND gate
7. The output of an AND gate is “1” only when:
(A) All inputs are “1”
(B) Any input is “1”
(C) All inputs are “0”
(D) Only first input is “1”
8. The output of an OR gate is “1” when:
(A) All inputs are “1”
(B) All inputs are “0”
(C) Any input is “1”
(D) First input is “0”
9. A NAND gate is equivalent to:
(A) AND gate followed by NOT
(B) OR gate
(C) NOR gate
(D) XOR gate
10. A flip-flop is used to:
(A) Generate AC
(B) Amplify signals
(C) Store a single bit of data
(D) Convert DC to AC
11. A D flip-flop stores:
(A) Data at the clock edge
(B) Always 0
(C) Always 1
(D) Sum of inputs
12. A JK flip-flop differs from a SR flip-flop because:
(A) It does not have an invalid state
(B) It has more outputs
(C) It is analog
(D) It cannot toggle
13. The main function of a counter is to:
(A) Generate sinusoidal signal
(B) Store voltage
(C) Switch current
(D) Count pulses or events
14. A 4-bit binary counter can count up to:
(A) 15
(B) 16
(C) 8
(D) 10
15. A multiplexer (MUX) is used to:
(A) Generate pulses
(B) Store data
(C) Amplify voltage
(D) Select one input from many and forward it to output
16. A demultiplexer (DEMUX) is used to:
(A) Route a single input to one of many outputs
(B) Store bits
(C) Convert AC to DC
(D) Amplify signals
17. An ADC (Analog to Digital Converter) converts:
(A) Analog signals to digital signals
(B) Digital to analog
(C) AC to DC
(D) Voltage to current
18. A DAC (Digital to Analog Converter) converts:
(A) Analog to digital
(B) Digital signals to analog signals
(C) AC to DC
(D) High voltage to low voltage
19. Industrial electronics commonly uses:
(A) Sensors, PLCs, and drives
(B) Only resistors and capacitors
(C) Only transformers
(D) Only batteries
20. A PLC (Programmable Logic Controller) is used for:
(A) Automating industrial processes
(B) Generating AC
(C) Converting DC to AC
(D) Measuring voltage only
21. A TRIAC is used in:
(A) Transformers
(B) DC generation
(C) AC switching and control
(D) Relays
22. A SCR (Silicon Controlled Rectifier) is used for:
(A) Controlled rectification
(B) Signal amplification
(C) Voltage step-up
(D) Frequency change
23. In industrial drives, speed control is achieved by:
(A) Changing conductor size
(B) Varying supply voltage or frequency
(C) Changing insulation
(D) Changing resistance only
24. A common sensor used in industrial automation is:
(A) Proximity sensor
(B) Fuse
(C) Switch
(D) Resistor
25. TTL logic gates operate at:
(A) 220 V
(B) 12 V
(C) 24 V
(D) 5 V
26. CMOS logic gates are preferred because:
(A) Low power consumption
(B) High voltage only
(C) High current only
(D) Fast AC switching
27. In digital electronics, a clock signal is used to:
(A) Step up voltage
(B) Supply power
(C) Synchronize operations of circuits
(D) Reduce current
28. A buffer gate is used to:
(A) Strengthen signal without changing logic
(B) Invert signal
(C) Convert analog to digital
(D) Store data
29. A Schmitt trigger is used to:
(A) Store data
(B) Generate sinusoidal signal
(C) Eliminate noise from digital signals
(D) Amplify current
30. A binary half adder adds:
(A) Two single-bit numbers
(B) Three numbers
(C) Only carry
(D) Only sum
31. A full adder adds:
(A) Only two bits
(B) Two bits and a carry input
(C) Only sum
(D) Only carry
32. Inverters are widely used in:
(A) DC-AC conversion
(B) AC-DC conversion
(C) Step-up transformers
(D) Motors only
33. Industrial electronics improves:
(A) Efficiency and control of machines
(B) Voltage only
(C) Frequency only
(D) Load only
34. Industrial drives use:
(A) Only switches
(B) Only resistors
(C) Only transformers
(D) DC drives, AC drives, and VFDs
35. A relay in industrial electronics is used to:
(A) Switch loads electrically
(B) Step up voltage
(C) Reduce current
(D) Store energy
36. The main purpose of industrial control panels is:
(A) Increase frequency
(B) Step up voltage
(C) Step down current
(D) Safe and centralized control of machinery
37. A PLC input can be:
(A) Digital or analog
(B) Only voltage
(C) Only current
(D) Only resistive
38. A PLC output can be:
(A) Only digital
(B) Digital, analog, or relay operated
(C) Only analog
(D) Only relay
39. Digital electronics use:
(A) Logic levels to represent data
(B) Continuous voltage only
(C) AC signals only
(D) DC signals only
40. Industrial sensors convert physical quantity into:
(A) Chemical signals
(B) Mechanical signals
(C) Electrical signals
(D) Thermal signals
41. H-bridge circuits are used to:
(A) Control direction of DC motors
(B) Measure voltage
(C) Measure current
(D) Step up AC
42. Logic families include:
(A) Resistor, capacitor
(B) AC, DC only
(C) TTL, CMOS, ECL
(D) Transformer only
43. Industrial electronics reduces:
(A) Human intervention in repetitive processes
(B) Voltage
(C) Current
(D) Frequency
44. A SCR gate turn-off requires:
(A) Increase of current
(B) Increase of voltage
(C) Reduction of current below holding current
(D) AC input only
45. Opto-isolators are used for:
(A) Electrical isolation between circuits
(B) Power conversion
(C) Voltage amplification
(D) Frequency modulation
46. A bistable multivibrator is:
(A) Counter
(B) Oscillator
(C) Amplifier
(D) Flip-flop storing one bit
47. Industrial electronics controllers improve:
(A) Accuracy and repeatability
(B) Voltage only
(C) Frequency only
(D) Load only
48. A logic XOR gate output is “1” when:
(A) All inputs “1”
(B) Inputs are same
(C) All inputs “0”
(D) Inputs are different
49. Digital timers in industrial circuits are used for:
(A) Delayed operations
(B) Voltage step-up
(C) Load monitoring only
(D) Frequency measurement
50. PLC programming languages include:
(A) Only Java
(B) Only C programming
(C) Ladder logic, function block, structured text
(D) Only Python