Two marks questions and answers

TWO MARKS QUESTIONS AND ANSWERS

1. Why are electrical-controls of fluid power systems preferred than the manual controls?

Because electrical controls offer the following features:

(i) They can be easily controlled.

(ii) They improve the overall control flexibility of fluid power systems.

(iii) They provide quick and accurate control operations.

(iv) They require less maintenance.

2. List any four basic types of electric switches used in electrically controlled fluid power circuits.

1. Push-button switches,

2. Limit switches,

3. Pressure switches, and

4. Temperature switches.

3. What is the use of a push-button switch ?

The push-button switch is primarily used for starting and stopping of the machinery. 

4. What are limit switches? How do they differ from push-button switches ?

• The limit switches are used to identify the extreme limits of the cylinder actuation. 

• Difference: The difference between the push-button and limit switches is that push- button switches are actuated manually whereas the limit switches are mechanically actuated devices.

5. What is the purpose of a pressure switch?

The pressure switches are used to sense a change in pressure automatically, and opens or closes an electrical switch when a predetermined pressure is reached.

6. What is the use of a temperature switch ?

The temperature switches are used to sense a change in temperature automatically, and opens or closes an electrical switch when a predetermined temperature is reached.

7. Differentiate pressure switch and temperature switch.

• Pressure switch is used to sense a change in pressure automatically, and opens or closes an electrical switch when a predetermined pressure is reached.

• Temperature switch is used to sense a change in temperature automatically, and opens or closes an electrical switch when a predetermined temperature is reached.

8. What is a solenoid? Also state its use.

• A solenoid is an electromagnetic mechanical transducer that converts an electrical signal into a mechanical output force.

• Solenoids provide a push or pull force to remotely operate fluid power valves.

9. What are relays? (or) What do you mean by electrical relays ? 

Relays are nothing but electrically operated switches. The electrical relays offer simple ON/OFF switching action in response to a signal issued by a control system. Relays are commonly used to open or close the contacts and thereby energize or de-energize solenoids which operate at a high current level.

10. What are the purpose of timers?

Timers, also known as time-delay relays, are time delay switches used to control the time duration of a working cycle.

11. When to use timer and relay? Why?

• Timers are time delay switches used to control the time duration of a working cycle. 

• Timers are commonly applied in electrical control circuits when a time delay from the instant of actuation to the closing of contacts is required.

12. Draw the graphic symbols for the following:

(a) Solenoid, and (b) Indicator lamp.

13. What is a ladder diagram?

A ladder diagram is nothing but an electrical diagram showing the hardware connections between the various electrical control devices.

14. List the uses of ladder diagrams.

Ladder diagrams provide a circuit designer with a practical means to examine input process and output functions to quickly plan the circuit layout design for a particular hydraulic or pneumatic application.