The question asks about the energy transformation that occurs in an electric motor. To answer this, we need to understand the fundamental principle of how an electric motor operates.
Correct Option: D) From electrical to mechanical
The question asks to identify the incorrect statement about magnetic field lines. We need to evaluate each option based on the fundamental properties of magnetic field lines.
Correct Option: C) If magnetic field lines are parallel and equidistant, they represent zero field strength.
This statement is incorrect. Parallel and equidistant magnetic field lines represent a uniform magnetic field, meaning the field strength is constant and non-zero in that region.
The question asks for the unit of luminous intensity. This is a direct recall question from the fundamental units in physics, specifically photometry.
C) Candela is the SI unit of luminous intensity. Luminous intensity is a measure of the wavelength-weighted power emitted by a light source in a particular direction per unit solid angle. The candela is one of the seven SI base units.
The question asks for the unit that measures the total amount of visible light emitted by a source. This refers to the total luminous flux, which is a measure of the perceived power of light.
Correct Option: B) Lumen is the SI unit of luminous flux, which quantifies the total amount of visible light emitted by a source, as perceived by the human eye.
The question asks about the gas commonly used in fluorescent tubes. Fluorescent tubes work on the principle of gas discharge, where an electric current passes through a gas, causing it to emit ultraviolet (UV) light. This UV light then strikes a phosphor coating inside the tube, which converts it into visible light. The choice of gas is crucial for efficient UV production.
C) Mercury Vapor is the primary gas responsible for emitting ultraviolet radiation in fluorescent tubes, which then excites the phosphor coating to produce visible light.
The question asks about the typical efficiency range of LED lights. Efficiency in lighting refers to how effectively electrical energy is converted into visible light, often measured in lumens per watt (lm/W) or as a percentage of energy converted to light versus heat. We need to identify the range that best represents modern LED technology.
Correct Option: D) 80-90%