Electrical Apparatus and Safety: Measurement of Voltage and Current
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Questions and Answers

What is the symbol for current?

  • C
  • V
  • E
  • A (correct)

    • How should an ammeter be connected to measure current?

  • In series with the load (correct)
  • Across the load
  • In parallel with the load
  • In parallel with the voltage source

    • What problem may occur if an ammeter is connected in parallel with a circuit component?

  • Increased resistance
  • Reduced voltage
  • Short-circuit current (correct)
  • Decreased current

    • What is the unit of voltage?

    <p>Volts</p> Signup and view all the answers

    Why is it important for ammeters to have low internal resistance?

    <p>To not alter the current in the circuit</p> Signup and view all the answers

    What causes waveform error in MI instruments?

    <p>The effect of inductance on the eddy current</p> Signup and view all the answers

    Why is the fixed coil of the electrodynamometer wattmeter split into two parts?

    <p>To allow the load current to flow through it</p> Signup and view all the answers

    What type of control system does the Electrodynamometer Wattmeter use?

    <p>Spring control system</p> Signup and view all the answers

    What is the purpose of the knife-edge pointer in electrodynamometer wattmeters?

    <p>To eliminate parallax error</p> Signup and view all the answers

    What is the major disadvantage of the Dynamometer Type Wattmeter at low power factors?

    <p>Errors due to inductance in the potential coil</p> Signup and view all the answers

    What is a major advantage of the PMMC instrument?

    <p>High torque to weight ratio</p> Signup and view all the answers

    Why is the body of the electrical equipment not connected to the supply neutral directly?

    <p>Long transmission lines increase resistance</p> Signup and view all the answers

    Which application is NOT listed for the PMMC instrument?

    <p>Wattmeter</p> Signup and view all the answers

    What is the primary purpose of electrical earthing?

    <p>To protect equipment from damage</p> Signup and view all the answers

    What is a key advantage of plate earthing over pipe earthing?

    <p>Lower maintenance</p> Signup and view all the answers

    Why is connecting a voltmeter in parallel important in a circuit?

    <p>To minimize the loading effect</p> Signup and view all the answers

    What is the purpose of the high internal resistance in voltmeters?

    <p>To draw as little current from the circuit as possible</p> Signup and view all the answers

    How does a repulsion type instrument function in measuring current?

    <p>By generating a force of repulsion between two magnetized vanes</p> Signup and view all the answers

    Why are moving iron instruments considered robust?

    <p>Because of simple construction and stationary current-carrying parts</p> Signup and view all the answers

    What is a disadvantage of moving iron instruments in terms of accuracy?

    <p>They have a non-uniform scale</p> Signup and view all the answers

    What is the purpose of the aluminum former in the PMMC instrument?

    <p>To produce damping torque</p> Signup and view all the answers

    Which material are the permanent magnets in the PMMC instrument made of?

    <p>Alnico</p> Signup and view all the answers

    What is the role of the control spring system in the PMMC instrument?

    <p>To produce controlling torque</p> Signup and view all the answers

    How does the PMMC instrument reach a steady-state position?

    <p>Through the action of eddy currents on the aluminum former</p> Signup and view all the answers

    What is the role of the mirror and proper alignment of the pointer blade in the PMMC instrument?

    <p>To reduce parallax error</p> Signup and view all the answers

    What is the main component of the driving system in a single-phase energy meter?

    <p>Electromagnet</p> Signup and view all the answers

    What is the purpose of the braking system in an energy meter?

    <p>To reduce the rotation of the aluminium disc</p> Signup and view all the answers

    How is the movement of the aluminium disc controlled in an energy meter?

    <p>By shifting the permanent magnet position</p> Signup and view all the answers

    What is the role of the register system in an energy meter?

    <p>To record the number of disc rotations</p> Signup and view all the answers

    What does the PMMC instrument measure in an energy meter?

    <p>Current</p> Signup and view all the answers

    What is the purpose of pouring water in the Plate Earthing system?

    <p>To maintain the earth electrode resistance value below 5 ohms</p> Signup and view all the answers

    In Pipe Earthing, why is a mixture of salt and coal filled around the GI pipe?

    <p>To keep the value of the earth resistance at the desired level</p> Signup and view all the answers

    Why are insulated tools recommended while working with electricity?

    <p>To avoid getting a severe shock</p> Signup and view all the answers

    Why should all electric connections at switches, plugs, sockets, and junctions be tight?

    <p>To reduce the dangers of any accidental shocks</p> Signup and view all the answers

    What should be done immediately in the case of a short-circuit or accidental contact with a live wire?

    <p>Provide support of non-conducting material</p> Signup and view all the answers

    How can you decrease the danger of any accidental shock?

    <p>Properly earth all electrical appliances</p> Signup and view all the answers

    What is the purpose of avoiding contact with water while working with electricity?

    <p>To improve safety</p> Signup and view all the answers

    Why must fuses and switches be connected in the live wires?

    <p>To reduce the risk of fires</p> Signup and view all the answers

    What should be done if a person has accidentally contacted a live wire?

    <p>Immediately turn off the main switch</p> Signup and view all the answers

    Why is it recommended to use rubber gloves and goggles while working on any electrical circuit?

    <p>To ensure personal safety</p> Signup and view all the answers

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