Transformer MCQs March 15, 2021 By WatElectronics This article lists 100 Transformer MCQs for engineering students. All Transformer Questions & Answers given below include a hint and wherever possible link to the relevant topic. This is helpful for users who are preparing for their exams, interviews, or professionals who would like to brush up their fundamentals on Transformers topic which is core in Electronics & Electrical Engineering. A transformer is a static device, which works on the principle of Faraday’s law of electromagnetic induction. The basic functionality of a transformer is to transfer electrical energy from one circuit to another. It mainly consists of two windings namely primary and a secondary winding, based on the number of turns on either side of windings, the transformer is classified into two types step up and step-down transformer. If the number of turns is more on the secondary winding of a transformer it is called a step-up transformer and if the number of turns is more on the primary winding of a transformer it is called a step-down transformer. Transformers are further classified based on their voltage levels used, the type of core used, the number of windings used, etc. The merits and demerits of a transformer are it operates with higher efficiency and occupies more space with high maintenance cost. Some of the applications of a transformer are regulators, power supply appliances, voltage converter. Transformer Multiple Choice Question & Answers 1). Transformer works on ______ principle. a) Gauss’s law b) Fleming’s right-hand rule c) Faraday’s law of electromagnetic induction d) Fleming’s left-hand rule None Hint 2). A step-up transformer has _____ number of turns on primary winding and _____ number of turns on secondary winding. Add description here! Less, More More, More More, Less Less, Less None Hint 3). A step-down transformer has _____ number of turns on primary winding and _____ number of turns on secondary winding. Less, More More, Less More, More Less, Less None Hint 4). A transformer is a _____ device. Static Dynamic Static and Dynamic None of the above None Hint 5). In a current transformer _____ winding is closed. Primary Secondary Both a & b None of the above None Hint 6). In a transformer the relation between the input frequency and the output voltage on secondary winding is _____. Same Increases Decreases Increases and decreases with time None Hint 7). The efficiency of a power transformer is _____ at full load. Same Minimum Maximum Fluctuates None Hint 8). Copper losses in a transformer are measured using _____. Closed circuit Open circuit Both a & b None of the above. None Hint 9). Transformer core lamination is made up of _____. Silicon steel Cast steel Cast iron Aluminium None Hint 10). What is the functionality of a breather in a transformer? It absorbs the moisture of air during breathing Passes cold air to the transformer It is the transformer oil filter Both a & b None Hint 11). What is basic functionality of a transformer? Voltage to current converter Current to voltage converter Frequency converter None of the above None Hint 12). What are the two types of Instrument transformer? Voltage transformer Current transformer Potential transformer Both b and c None Hint 13). The core of a transformer is laminated for _____ reason Minimize hysteresis loss Minimize eddy & hysteresis current loss Lowers eddy current loss Copper loss None Hint 14). The voltage regulation in a transformer is said to be negative when the load power factor is _____. Ideal Lags Leads Infinity None Hint 15). What is the need of performing a short circuit test in a transformer? To find copper loss To find core loss To find insulation resistance To find complete loss None Hint 16). Which losses in a transformer is zero at full load? Core loss Eddy current loss Copper loss Friction loss None Hint 17). A transformer has _____ resistance between its primary and secondary winding. Infinity 0 0.1 ohm 100 ohm None Hint 18). The current rating of a transformer is expressed as_____. Kilowatts KVAR Kilo-volt-ampere Ampere None Hint 19). What is the purpose of oil in an oil-filled transformer? Insulate Resistance Cooling Both a & d None Hint 20). Which test is used to determine iron losses in a transformer? SC test OC test Both SC & OC None of the above None Hint 21). Which of the following component is not related to the transformer? Breather Conservator Buchholz relay Exciter None Hint 22). Which component of the transformer causes noise? Vibration due to mechanical motion Fan that is used for cooling purpose Iron core which contains magnetostriction All the above None Hint 23). The relation between primary and secondary flux in a transformer is ________. Primary is greater than the secondary flux Primary flux is less than the secondary flux Primary flux and secondary flux are equal None of the above None Hint 24). If the direct current is supplied to a transformer, what happens to a transformer. Transformer operates normally Transformer operates with greater efficiency Transformer operates with low efficiency Transformer stops working due to damage that occurred None Hint 25). How much percent of friction loss is present in a transformer? 1% 3% 0% 5% None Hint Transformer Interview Questions 26). Which transformer has primary and secondary winding coupled electrically and magnetically? Power transformer Current transformer Potential transformer Auto transformer None Hint 27). What is the purpose of stones in a transformer? To provide Insulation To safeguard from fire accident if there was an oil leakage in a transformer To prevent the growth of weeds and plant All the above None Hint 28). What is the reason behind the cruciform shape of a transformer? Decrease in core loss Decrease in the reluctance of the core Decrease in copper winding All the above None Hint 29). Which losses are neglected when a transformer undergoes a short circuit test? Copper losses Core loss Eddy current loss Hysteresis loss None Hint 30). The volatility and viscosity values of an oil transformer should be _________. High, Low Low, High Low, Low High, High None Hint 31). On which parameter does the core size of a transformer depends? Cores area and frequency Only core area Only frequency None of the above None Hint 32). Formula to calculate the number of turns ratio in a transformer is given as_____. Number of turns of secondary / Number of turns of the primary Number of turns of primary / Number of turns of secondary Number of turns of secondary alone Number of turns of primary alone None Hint 33). Formula for primary voltage of a transformer is _________. Primary voltage (Vp)*turns ratio (n) Secondary voltage (Vs)* turns ratio (n) Primary voltage(Vp) * efficiency Primary voltage(Vp) * secondary voltage(Vs) None Hint 34). Formula for secondary voltage of a transformer is _________. Primary voltage (Vp)/turns ratio (n) Secondary voltage (Vs)* turns ratio (n) Primary voltage(Vp) * efficiency Primary voltage(Vp) * secondary voltage(Vs) None Hint 35). The phase angle of an ideal transformer is ________. ΦP ≡ ΦS Φp > φs Φp < φs Φp != φs None Hint 36). What is a dual voltage transformer? A transformer with a single primary and single secondary windings A transformer with two primaries and two secondary windings A transformer with single primary and dual secondary windings None of the above None Hint 37). Which of the following is the advantage of a transformer? It is a stationary device It provides high efficiency No starting time is required All the above None Hint 38). Which of the following is the disadvantage of a transformer? It is a stationary device It is a bulky device Size and voltage Both b and c None Hint 39). What are the types of cores in a transformer? Core Type Shell type Ideal type Both a and b None Hint 40). Which test is performed to find the temperature of a transformer? Open load test Close load test Sumpner’s test None of the above None Hint 41). The maximum efficiency of a transformer can be observed at _____ condition. Maximum Iron loss Minimum core loss Copper loss and iron loss are equal Hysteresis loss None Hint 42). What is the maximum range the natural oil cooling can be used in a transformer? 50kVA 3000kVA 500 kVA 250kVA None Hint 43). What is the equivalence resistance relationship between the primary and secondary winding of a transformer? R2/VI R2/K2 R2 R1 None Hint 44). On which side of transformer tapings are provided in general? Secondary side Right side Low voltage side Primary side None Hint 45). Which substance is used in the transformer breather component? Silica gel Sodium Silica sand Potassium None Hint 46). What is the value of inductance in an ideal transformer? 0 Infinity 100% 50% None Hint 47). Give the equation of hysteresis loss in a transformer CBmax= Bmax CBmax=Bmax 1-6 CBmax=0 None of the above None Hint 48). The core of a transformer is constructed using ________. Wood Zinc Steel Silicon steel None Hint 49). What is the purpose of a conservator in a transformer? Protects against short circuit Prevents moisture entry Controls the transformer oil which expands and contracts based on environmental temperature None of the above None Hint 50). The lamination thickness of a transformer is______. 0.4 mm to 0.5 mm 0.1mm to 0.2 mm 2.5 mm to 5 mm 6 mm to 8 mm None Hint Transformer Questions and Answers 51). The oil used in a transformer must be free from______. Sand Odour Moister Sludge None Hint 52). On which transformer can we install the Buchholz relay? Power transformer Mechanical transformer Oil cooled transformer Welding transformer None Hint 53). Why do harmonics occur in a transformer? Short circuit Break down Less insulation core getting saturated None Hint 54). What is the efficiency of the distribution transformer? 100% 50% 10 % 99% None Hint 55). A transformer connected in star fashion works at ______ condition. No load Full load Balanced load and unbalanced load Balanced load None Hint 56). Buchholz relays warns about______. Electrical faults that occur within the transformer Electrical faults that occur in the surroundings of a transformer Both a and b None of the above None Hint 57). Why transformers magnetized current is small? Due to little air gap Due to flux leakage Due to lamination None of the above None Hint 58). Which parameter in a transformer remains the same? Voltage Frequency Resistance All the above None Hint 59). On which side helical coil in a transformer is placed? On less voltage side of a HkVA transformer Power transformer Voltage transformer Ideal transformer None Hint 60). Which test is least done on a transformer? Radio interface test OC test SC test None of the above None Hint 61). What happens if harmonics occur in a transformer? Core losses increases I2R losses increases Both a and b None of the above None Hint 62). Which type of core is used in a transformer with high frequency? CU core Cast Fe core Air core None Hint 63). The emf equation of a transformer has _____ value of flux. Maximum Minimum Equal Zero None Hint 64). The purpose of Silicon steel in a transformer is to __________. Increase eddy current loss Reduce hysteresis loss Maintain eddy current losses None of the above None Hint 65). Less cross-sectional area in a transformer can be observed on ________. Primary side High voltage side Secondary side None of the above None Hint 66). At what conditions does power transformer has max efficiency Full load No load Half load None of the above None Hint 67). What is the advantage of autotransformer over dual transformer? Low power Less winding materials Half load None of the above None Hint 68). SI units of EMF Volts Amperes Hertz Centimetres None Hint 69). SI unit of power Watt Hz Centimetres Joule None Hint 70). Units of electric field Volts Amperes Volts / Meter Centimetres None Hint 71). What is Np in a transformer? Number of turns on the primary winding Number of turns on the secondary winding Number of turns on both primary and secondary winding None of the above None Hint 72). What is Ns in a transformer? Number of turns on the primary winding Number of turns on the secondary winding Number of turns on both primary and secondary winding None of the above None Hint 73). SI unit of magnetic field strength Volts Amperes Amp / Meter Centimetres None Hint 74). SI unit of Electrical Flux Volt Meter Amperes Amp / Meter Centimetres None Hint 75). Faradays Law equation E = N dφ / dt E = N dφ E = N dt N dφ = dt None Hint Transformer Online Test 76). Transformers are classified based on __________. Core used Voltage level Number of windings All the above None Hint 77). Which of the following is the property of an ideal transformer? Absence of losses Absence of magnetic leakage 10-ohm resistance Both a and b None Hint 78). When a transformer is operated at rated voltage and low frequency what happens? There will be an increase in core flux Increase in resistance value Increase in current value None of the above None Hint 79). At what condition does an ideal transformer gives maximum efficiency? Copper loss = 0 Copper loss = infinity Copper loss = iron loss Copper loss = 99% None Hint 80). What happens to iron loss in a transformer, if there is an increase in input frequency? Add description here! 0 Infinity Increases Decreases None Hint 81). If the negative voltage obtained from a load of a transformer, what does it mean?81) If the negative voltage obtained from a load of a transformer, what does it mean? Capacitive type load Inductive type load Resistive type load None of the above None Hint 82). Transformer with a low power factor is used to measure _____ losses. Iron losses Steel losses Eddy current losses None of the above None Hint 83). Which material is used between the transformer’s laminations? Mica strip Varnish Oil None Hint 84). A sandwich-type winding is used in which phase shell type transformer? Single phase Three-phase Two-phase Zero phase None Hint 85). Why is the OC test is performed on the transformer? To find hysteresis loss To find efficiency To find resistance To find core loss None Hint 86). Why is the SC test is performed on the transformer? To find copper loss To find efficiency To find resistance To find core loss None Hint 87). A single-phase transformer operating parallelly should maintain _________. Equal polarity Opposite polarity Equal efficiency None of the above None Hint 88). A transformer should have _____ volatility. Low Equal High zero None Hint 89). A transformer should have _____ viscosity. Low Equal High zero None Hint 90). Which winding of the current transformer is short-circuited? primary secondary both a and b none of the above None Hint 91). Natural air cooling property in a transformer is restricted _____ limit. 0 MVA 1 MVA Upto 1.5 MVA 5 MVA None Hint 92). Which type of transformer has less magnetic leakage? Core type Shell type Both a and b None of the above None Hint 93). A transformer operating at what condition it gives maximum efficiency at a unity power factor? Constant load current Constant load voltage Constant frequency Zero None Hint 94). Which material is used to withstand high temperatures in a transformer? Silicon Steel Mica Glass None Hint 95). Which component is visible from outside a transformer? Windings Core Wires Brushes None Hint 96). What is the noise produced by a transformer called? Hum Zoom Buzz Huzz None Hint 97). Why does hum occurs in the transformer? Due to full load Due to no load Due to magnetostriction Due to the vibrations None Hint 98). What happens to transformer windings if operated continuously? Temperature increases Temperature decreases Resistance increases None of the above None Hint 99). Which part of the transformer is damaged by overheating? Core Frame Winding insulation Brushes None Hint 100). What is the relationship between minimum voltage regulation and the power factor of the load? Lags Leads Zero Infinity None Hint Time's up
