IOCL Junior Operator Solved Questions & Answers || IOCL Junior Operator General Science Questions and Answers

• Recording instruments provide a continuous record of an electrical quantity’s variations over a period of time, typically on graph paper.
• This recorded data allows users to go back and check the value of the quantity at any specific point in time.
• Indicating instruments only show the present value, and integrating instruments only show the total accumulated value over a period

• Secondary instruments can be classified according to the effects of electricity they utilize.
• Secondary instruments can be classified based on the effects of electric current or voltage that their operation depends on.
• These effects include magnetic, heating, chemical, electrostatic, and electromagnetic induction.
• For example, ammeters and voltmeters can utilize the magnetic or heating effect, while DC ampere-hour meters use the chemical effect.
• The classification of secondary instruments can also be based on their function (indicating, recording, or integrating) or the kind of current they measure (AC, DC, or AC/DC)

• The effects of electric current used in various instruments include magnetic, heating, chemical effects,  electrostatic effect, and electromagnetic induction effect.
• Gravitational effect is not directly related to the functioning of electrical instruments.

An indicating instrument requires three essential torques/forces to function correctly:

1. Deflecting torque
2. Controlling torque
3. Damping torque

• Deflecting torque moves the pointer.
• Controlling torque opposes the deflecting torque and brings the pointer back to zero when there is no measurement.
• Damping torque minimizes oscillations of the pointer so it settles quickly

• The deflecting force in an instrument causes the moving system to move from its zero position.
• The deflecting force or torque is the force that initiates the movement of the pointer (or moving system) from its initial resting position (usually zero) on the scale of the indicating instrument.
• This force is produced by the electrical signal being measured and causes the pointer to move proportionally to the magnitude of that signal (current).

• The controlling force acts in opposition to the deflecting force.
• It returns the pointer to zero when the deflecting force is removed.
• Without a controlling force, the pointer would swing uncontrollably

• A method of producing controlling force is Gravity control.
• Controlling force in indicating instruments can be produced by two methods: spring control and gravity control.
• Spring control uses springs to provide the controlling torque.
• Gravity control uses the force of gravity acting on a weight attached to the moving system to provide the controlling torque.
• Damping control is related to damping force, not controlling force.

• The gravity controlled instruments must be used in Vertical position,
• Gravity control relies on the force of gravity acting on a weight to provide the controlling torque.
• For this mechanism to work correctly, the instrument must be oriented vertically.
• Otherwise, the weight will not exert the proper opposing force, leading to inaccurate readings

• The springs used in controlling mechanisms are typically made of Phosphor-bronze or beryllium-copper.
• Springs for controlling mechanisms often utilize phosphor bronze because it is non-magnetic, has a low-temperature coefficient, and has low specific resistance.
• While steel alloys can be used in springs for various applications, phosphor bronze is specifically noted for its suitability in control systems.

• In instrument control mechanisms using two springs, the springs are indeed wound in opposite directions.
• In measuring instruments like ammeters or voltmeters, two springs (A and B) are used to ensure the needle shows an accurate reading.
• These springs are wound in opposite directions.

• When the needle rotates, one spring (let’s say A) winds up, while the other spring (B) unwinds.
• Together, these springs create a force that tries to return the needle to its original position.
• This force is known as the controlling torque.
• The torsional torque of these springs is directly proportional to the angle of rotation of the needle.
• This means the more the needle rotates, the greater the torsional force generated within the springs, and the greater the controlling torque applied