⚡ Electrical Engineering Solved MCQs with Answers

Practice 757 approved ⚡ Electrical Engineering questions with verified answers from the 🛠️ Engineering Essentials subject for Pakistan exams.

757 solved MCQs

An ohmmeter is connected across an inductor and the pointer indicates zero ohms. The inductor isAnswer: shorted Two inductors, L1 and L2, are in parallel. L1 has a value of 25 H and L2 a value of 50 μH. The parallel combination is in series with L3, a 20 μH coil. The entire combination is across an ac source of 60 Vrms at 300 kHz. The total rms current isAnswer: 870 mA An inductor, a 1 k resistor, and a switch are connected in series across a 6 V battery. At the instant the switch is closed, the inductor voltage isAnswer: 6 V The winding resistance of a coil can be increased byAnswer: Increasing the number of turns or using thinner wire An inductance of 0.43 mH is smaller thanAnswer: 0.05 H An inductor and a resistor are in series with a sine wave voltage source. The frequency is set so that the inductive reactance is equal to the resistance. If the frequency is increased, thenAnswer: Vₗ > Vᵣ The current through a 120 mH coil is changing at a rate of 150 mA/s. The voltage induced across the coil isAnswer: 18 mV When the current through an inductor decreases, the amount of energy stored in the electromagnetic fieldAnswer: decreases Three 15 mH inductors are in series. The total inductance isAnswer: 45 mH An 18 V power supply is connected across a coil with a winding resistance of 180 Ω. Current flow in the coil isAnswer: 100 mA A switch, a 220 resistor, and a 60 mH inductor are in series across a 20 V battery. What is the current through the inductor two time constants after the switch is closed?Answer: 78 mA A 320 H coil is in series with a 3.3 k resistor. How long does it take for current to build up to its full value?Answer: 0.48 μs Five inductors are connected in series. The lowest value is 8 μH. If the value of each inductor is twice that of the preceding one, and if the inductors are connected in order of ascending values, the total inductance isAnswer: 248 μH The inductance of an iron-core coil decreases ifAnswer: The number of turns is decreased The following coils are in parallel: 75 μH, 40 μH, 25 μH, and 15 μH. The total inductance is approximatelyAnswer: 6.9 μH When the current through an inductor is cut in half, the amount of energy stored in the electromagnetic fieldAnswer: Is quartered What kVA rating is required for a transformer that must handle a maximum load current of 8 A with a secondary voltage of 2 kV?Answer: 16 kVA The turns ratio required to match an 80 Ω source to a 320 load isAnswer: 2 When the turns ratio of a transformer is 20 and the primary ac voltage is 12 V, the secondary voltage isAnswer: 240 V If a transformer has 50 turns in the primary winding and 10 turns in the secondary winding, what is the reflective resistance if the secondary load resistance is 250 Ω?Answer: 6,250 Ω A certain transformer has 400 turns in the primary winding and 2,000 turns in the secondary winding. The turns ratio isAnswer: 5 The primary winding of a transformer has 110 V ac across it. What is the secondary voltage if the turns ratio is 8?Answer: 880 V To step 110 V ac down to 20 V ac, the turns ratio must beAnswer: 0.18 The mutual inductance when k = 0.65, L1 = 2 μH, and L2 = 5 μH isAnswer: 2 μH If 25 W of power are applied to the primary of an ideal transformer with a turns ratio of 10, the power delivered to the secondary load isAnswer: 25 W A transformer with a 110 V primary has a 15:1 turns ratio. The load resistance, RL, is 120 Ω. What is the approximate voltage across the load?Answer: 7.3 V How many primary volts must be applied to a transformer with a turns ratio of 0.1 to obtain a secondary voltage of 9 V?Answer: 90 V In a certain loaded transformer, the secondary voltage is one-fourth the primary voltage. The secondary current isAnswer: four times the primary current A certain transformer has a turns ratio of 1 and a 0.85 coefficient of coupling. When 2 V ac is applied to the primary, the secondary voltage isAnswer: 1.7 V The primary coil of a transformer is connected to a 60 V ac source. The secondary coil is connected to a 330 Ω load. The turns ratio is 3:1. What is the secondary voltage?Answer: 20 V