Free Electrical Properties of Solids MCQs with Answers
32 Electrical Properties of Solids MCQs from Physics, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.
Electrical properties of solids depend on their band structure, charge carriers and conductivity. The topic compares conductors, insulators and semiconductors, relates resistivity to temperature, and covers intrinsic and extrinsic semiconductors, donor and acceptor impurities, electron and hole conduction, and the formation of p-type and n-type materials.
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32 questions · page 3 of 4
21. Metallic conduction involves the relatively free movement of their _ throughout the metallic lattice.
- A. Atoms
- B. Molecules
- C. Electrons
- D. Ions
Explanation: A is incorrect In metals atoms are not in combined form they are in electron pool type arrangementB is incorrect In metals molecules do not existC is correct since In metals electrons are in pool type arrangement and the can move within metal so the play their role in conductionD is incorrect because In metals ions are not present
Correct answer: Electrons22. The substances like germanium and silicon have:
- A. Negative temperature coefficients
- B. Positive temperature coefficients
- C. Both A and B
- D. None of the above
Explanation: Substances with a negative temperature coefficient of resistance, such as germanium and silicon, experience a decrease in resistance as temperature increases. This property is typical of semiconductors. Option A is correct. Option B describes metals, which have a positive temperature coefficient. Option C is incorrect because a material cannot simultaneously have both types of temperature coefficients. Option D is incorrect because germanium and silicon are correctly described by option A.
Correct answer: Negative temperature coefficients23. Carbon exists as allotropes, which are different crystalline or molecular forms of the same substance. Graphite and diamond are allotropes of carbon. Diamond is a non-conductor whereas graphite is a good conductor because:
- A. Graphite has a layered structure
- B. In graphite, all valence electrons are tetrahedrally bound
- C. In graphite one of valence electron is free to move
- D. Graphite is soft and greasy bound
Explanation: Graphite conducts electricity whereas diamond does not because in diamond the carbon atoms are bonded to other carbon atoms and all the valence electrons are bonded. whereas in graphite each carbon atom is only bonded to three other atoms. Therefore, there are delocalized (free) electrons in graphite due to 1 free valence electron in each carbon atom, which can move and carry a charge so graphite conducts electricity.
Correct answer: In graphite one of valence electron is free to move24. Which one of the following is the Boolean expression of the NAND gate?
- A. X = A.B
- B. B X = A + B
- C. X = Ā.B̄
- D. X = Ā + B̄
Explanation: The Boolean expression given for a NAND gate is that of logical addition and it is opposite to the AND gate The Boolean algebra for AND gate is X=A.B So, the Boolean algebra for the NAND gate is: X=A.B
Correct answer: X = Ā.B̄25. Which one of the following is the truth table of the NAND gate?
- A. Option A
- B. Option B
- C. Option C
- D. Option D
Explanation: The NAND gate, or "NotAND" gate, is the combination of two basic logic gates, the AND gate, and the NOT gate, connected in series. The output of a NAND gate is high when either of the inputs is high or if both inputs are low. In other words, the output is always high and goes low only when both inputs are high. The logic NAND function is given by the Boolean expression X=A.B. The truth table of a NAND gate is given below
Correct answer: Option B26. If signal is applied to input of non-inverting amplifier through resistance of 100kohm, and the value of feedback resistance is 10kohm, the gain is:
- A. 11
- B. 10
- C. 1.1
- D. 0.11
Explanation: The formula used for the gain in non inverting amplifier is given as: 1+(Feedback resistance/resistance of other resistor) 1+(10kohm/100kohm) 1+(0.1) 1.1 answer, this is gain.
Correct answer: 1.127. In metals, why does electric conductivity decrease with the increase of temperature?
- A. Because electron movement decrease with the increase of temperature
- B. Because metal ions oscillations hinder electron movement
- C. Because electron direction changes at high temperature
- D. Because they pass heat current through collision of electrons
Explanation: The correct option is B because metal ion oscillations hinder electron movement. As temperature increases, the vibrational motion of metal ions disrupts the movement of electrons, reducing electrical conductivity in metals.
Correct answer: Because metal ions oscillations hinder electron movement28. The resistance of the pure semiconductor decreases in a certain ratio with the?
- A. Decrease in temperature
- B. Increase in current
- C. Increase in temperature
- D. Decrease in current
Explanation: In a pure semiconductor, the resistance decreases with an increase in temperature. This happens because as temperature increases, some electrons in the valence band gain enough energy to jump to the conduction band, leaving behind holes in the valence band. This increases the number of charge carriers in the material, leading to a decrease in resistance.
Correct answer: Increase in temperature29. Metals are good conductors of electricity because they contain:
- A. Large number of freely mobile electrons
- B. A large number of bound electrons
- C. A small number of free electrons
- D. A small number of bound electrons
Explanation: Metals are good conductors of electricity because they contain a large number of freely mobile electrons.
Correct answer: Large number of freely mobile electrons30. The temperature at which the resistance of a conductor approaches zero is called
- A. Normal temperature
- B. Critical temperature
- C. Absolute temperature
- D. Curie temperature
Explanation: The temperature at which the resistance of a conductor approaches zero is called the critical temperature.
Correct answer: Critical temperature