1. A 3ɸ synchronous motors has been provided with damper winding. It can be started as a (a) Single phase synchronous motor. (b) 3ɸ squirrel cage induction motor. (c) 1ɸ induction motor. (d) 3ɸ alternator. [UPSSSC 2015] 2 Consider the following statements about a three-phase synchronous generator synchronized to an infinite bus when its mechanical […]
1. A DC cumulatively compounded motor delivers rated load torque at rated speed. If the series field is short-circuited, then the armature current and speed will (a) both decrease. (b) both increase. (c) increase and decrease respectively. (d) decrease and increase respectively. 2. A dc cumulatively compounded generator was operating satisfactorily and supplying power to
1. In a 3-phase power transformer, 5-limbed construction is adopted to (a) suppress the 5th and 7th harmonics. (b) suppress the 3rd and its multiple harmonics. (c) suppress all the orders of harmonics. (d) increase the capacity of the transformer. 2. Consider the following statements: The use of Delta-connected tertiary windings in star-star connected power
Tunneling Effect In a normally-doped P-N junction, the depletion layer is relatively wide and a potential barrier exists across the junction. The charge carriers on either side of the junction cannot cross over unless they possess sufficient energy to overcome this barrier (0.3 V for Ge and 0.7 V for Si). As is well-known, width
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Photodiode It is a two-terminal junction device which is operated by first reverse-biasing the junction and then illuminating it. A reverse-biased P-N junction has a small amount of reverse saturation current Is (or I0) due to thermally-generated electron-hole pairs. In silicon, Is is the range of nano-amperes. The number of these minority carriers depends on
Digital Frequency Meter An instrument which displays the frequency of a periodic electrical signal is known as digital frequency meter. The block diagram of a digital frequency meter system, shown in Figure 1 consists of an amplifier or an attenuator to which the input signal is applied. This performs the function of amplification or attenuation
Multimeter is a device used to measure multiple quantities in a circuit. The digital multimeters (abbreviated as DMM) have many advantages in comparison to analog multimeters. DMMs give highly precise results, have high input impedance, much greater resolution and are smaller in size. They indicate overload and show negative sign for reverse connection, and can
An instrument which is used to measure magnetic flux density is known as magnetometer. This instrument is also known as Gauss meter or Tesla meter since its output can be expressed in Gauss or Tesla. Gauss is the unit of magnetic flux density in CGS system while Tesla is in SI system. The two units
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Varactor Diode The varactor diode is a semiconductor, voltage-dependent variable capacitor alternatively known as varicap or voltacap or voltage-variable capacitor (VVC) diode. Basically, it is just a reverse-biased junction diode whose mode of operation depends on its transition capacitance (CT). We know that the reverse-biased junctions behave like capacitors whose capacitance is ∝ 1/VRn where
Oscilloscope Probes A probe is a conductor used to establish a connection between the circuit under test and the measuring instrument. While connecting the test circuit, the probe does not alter, load or disturbs the circuit and signal conditions to be analyzed. The probe should have high impedance. The probe bandwidth should be as high