Which one of the following statements is not correct ?

[amp_mcq option1=”An electric motor converts electrical energy into mechanical energy.” option2=”An electric generator works on the principle of electromagnetic induction.” option3=”The magnetic field at the centre of a long circular coil carrying current will be parallel straight lines.” option4=”A wire with a green insulation is usually the live wire of an electric supply.” correct=”option4″]

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UPSC CDS-1 – 2022

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Statement D is incorrect because a wire with green (or green/yellow) insulation is typically the earth wire in an electric supply, not the live wire.

Standard electrical wiring colour codes are used to identify the different wires in a circuit: Live, Neutral, and Earth. These colours vary by region, but green or green/yellow is almost universally used for the Earth wire, while red or brown is common for the Live wire, and black or blue is common for the Neutral wire.

Statement A is correct as electric motors convert electrical energy into mechanical energy using the force on a current-carrying conductor in a magnetic field. Statement B is correct as electric generators produce electric current based on the principle of electromagnetic induction, where a changing magnetic field induces an electric current. Statement C is correct; inside a long circular coil (solenoid) carrying current, the magnetic field lines are parallel straight lines, indicating a uniform field.

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