📡 Electronics and Communication Engineering (ECE) Solved MCQs with Answers

Practice 406 approved 📡 Electronics and Communication Engineering (ECE) questions with verified answers from the 🛠️ Engineering Essentials subject for Pakistan exams.

406 solved MCQs

At room temperature, the current in intrinsic semiconductor is due toAnswer: holes and electrons Ferroelectric materials are those whichAnswer: have a permanent polarization Assertion (A): For Diamond, μr = 1 Reason (R): Diamond is a diamagnetic material.Answer: Both A and R are true and R is correct explanation of A If n denotes principal quantum number, the angular quantum number l = 0, 1... (n - 1).Answer: True Assertion (A): In a perfect capacitor, the current density is given by ω ∈0E0∈'rcos(ωt + 90°), where ∈r' is real part of dielectric constant. Reason (R): In a perfect capacitor, dielectric losses are zero.Answer: Both A and R are true and R is correct explanation of A If a piece of wood is placed in a magnetic fieldAnswer: the magnetic field will not be affected The number of valence electrons in donor impurity areAnswer: 5 In a true valence crystal, the bonding between the atoms is accomplished by the sharing of valence electrons.Answer: True Which of the following are donor impurities? 1. Gold 2. Phosphorus 3. Boron 4. Antimony 5. Arsenic 6. Induim Select the correct answer using the following codesAnswer: 2, 4, 5 At room temperature the current in an intrinsic semiconductor is due toAnswer: holes and electrons At room temperature the current in an intrinsic semiconductor is due toAnswer: holes and electrons Work function is the maximum energy required by the fastest electron at 0 K to escape from the metal surface.Answer: False The most commonly used semiconductor material isAnswer: silicon In which of these is reverse recovery time nearly zero?Answer: Schottky diode A transistor has a current gain of 0.99 in the CB mode. Its current gain in the CC mode isAnswer: 100 In an n channel JFET, the gate isAnswer: p type The amount of photoelectric emission current depends onAnswer: intensity of incident radiation Assertion (A): A p-n junction has high resistance in reverse direction. Reason (R): When a reverse bias is applied to p-n junction, the width of depletion layer increases.Answer: Both A and R are true and R is correct explanation of A At very high temperatures the extrinsic semi conductors become intrinsic becauseAnswer: band to band transition dominants over impurity ionization When a voltage is applied to a semiconductor crystal then the free electrons will flow.Answer: towards positive terminal Ferrite haveAnswer: low resistivity In a p type material the Fermi level is 0.3 eV above valence band. The concentration of acceptor atoms is increased. The new position of Fermi level is likely to beAnswer: 0.28 eV above valence band In an n-p-n transistor, the majority carriers in the base areAnswer: electrons An LED has a rating of 2 V and 10 mA. It is used along with 6V battery. The range of series resistance isAnswer: 400 Ω and above The number of doped regions in PIN diode isAnswer: 2 A transistor has two p-n junctions. The batteries should be connected such thatAnswer: one junction is forward biased and the other is reverse biased A silicon (PN) junction at a temperature of 20°C has a reverse saturation current of 10 pico Ampere. The reverse saturation current at 40°C for the same bias is approximately.Answer: 40 pA In a bipolar transistor the barrier potentialAnswer: 0.7 V across each depletion layer Recombination produces new electron-hole pairsAnswer: False An amplifier without feedback has a voltage gain of 50, input resistance of 1 kΩ and output resistance of 2.5 kΩ. The input resistance of the current shunt -ve feedback amplifier using the above amplifier with a feedback factor of 0.2 isAnswer: 1/11 kΩ