The question asks to identify the type of motor commonly used in electrical shaving machines. We need to evaluate the characteristics of each motor type listed in the options and determine which one best fits the requirements of a shaving machine.
A) Universal motor — Universal motors are ideal for electrical shaving machines because they can operate on both AC and DC power, provide high starting torque, and achieve high speeds in a compact size, which are all essential characteristics for such appliances.
The question asks about the function of an economizer in power plants. An economizer is a heat exchange device that improves the overall efficiency of a power plant by recovering waste heat.
D) feed water — An economizer is specifically designed to pre-heat the feed water entering the boiler using the waste heat from the flue gases. This process increases the efficiency of the boiler and the entire power plant.
The question asks to identify a high head turbine among the given options. Turbines are classified based on the head (height of water) and specific speed at which they operate. High head turbines are designed to work efficiently with a large difference in water level.
D) Pelton wheel turbine is an impulse turbine that operates efficiently under very high heads (typically above 200 meters) and low flow rates. It converts the potential energy of water into kinetic energy through a nozzle, which then strikes the buckets of the runner.
This problem can be solved using Ohm's Law, which states the relationship between voltage, current, and resistance in an electrical circuit. Ohm's Law is given by the formula \(V = IR\), where \(V\) is the voltage, \(I\) is the current, and \(R\) is the resistance.
Thus, the current drawn is 1 A.
C) 1 A — This is the correct current calculated using Ohm's Law.
The question asks to identify which type of rectifier can withstand the maximum voltage on the DC side. This relates to the power handling capacity and design of different rectifier technologies, particularly mercury arc rectifiers and modern semiconductor devices.
C) Steel tank rectifier — Steel tank rectifiers are robust, industrial-grade mercury arc rectifiers designed for very high power applications. Their construction allows for superior cooling and insulation, enabling them to withstand significantly higher DC voltages and currents compared to glass bulb or smaller mercury bulb types. They were commonly used in applications requiring thousands of volts and amperes.
The question asks about the approximate voltage drop at the cathode in an arc rectifier. This refers to the voltage required to sustain the arc discharge at the cathode surface, which is a characteristic property of such devices.
B) 6 to 7 volts. This range accurately represents the typical cathode voltage drop observed in arc rectifiers, which is crucial for sustaining the arc discharge and ensuring electron emission from the cathode.
The question asks to identify the device that converts sound waves into Audio Frequency (AF) signals. This involves understanding the basic function of common electronic components related to sound.
Correct Option: D) A microphone is a transducer that converts sound energy (acoustic waves) into electrical energy (AF signals). It does this by sensing pressure variations in the air caused by sound and converting them into corresponding electrical voltage or current variations.
The question asks which modulation technique provides noiseless reception. We need to understand the characteristics of different modulation types, especially their susceptibility to noise, to determine the best option.
Correct Option: C) Frequency modulation
Frequency modulation (FM) provides noiseless reception because the information is encoded in the frequency variations of the carrier wave, not its amplitude. Noise primarily affects the amplitude of the signal. An FM receiver uses a limiter circuit to remove any amplitude variations caused by noise, thus preserving the original frequency-modulated signal and resulting in a much cleaner, "noiseless" output.
The question asks to identify the basic logic gate that produces an output which is the complement (or inverse) of its input. We need to recall the function of each basic logic gate.
Correct Option: C) INVERTER gate
The INVERTER gate, also known as a NOT gate, takes a single binary input and produces an output that is the logical complement (inverse) of that input. If the input is \(A\), the output is \(\bar{A}\) (read as "A-bar" or "NOT A").
The question asks to identify the most commonly used semiconductor material. This is a factual question related to materials science and electronics. We need to recall the primary material used in the vast majority of semiconductor devices today.
A) silicon is the most commonly used semiconductor material. It is the foundation of modern electronics, including microprocessors, memory chips, and solar cells, largely due to its abundance, low cost, and ability to form a stable oxide layer (\(\text{SiO}_2\)) which is critical for device isolation and gate dielectrics.