Materials and Components – Section 3
|41.||In carbon resistor colour code, if the third band is of silver, it indicates|
|A.||that three zeros are to be added to indicate the resistance value|
|B.||multiplier is 0.01|
|C.||multiplier is 0.1|
|D.||tolerance is ± 5%|
|42. ||In a metal, the drift velocity of electrons in the presence of a electric field E is|
|A.||proportional to E|
|B.||proportional to E|
|C.||inversely proportional to E|
|D.||proportional to E2|
Answer: Option A
Drift velocity is proportional to field strength.
|43. ||At a temperature of about 1 K, aluminium is a|
|44. ||An electron is moving in a circular orbit of radius R at angular velocity ω0 in a field free space. If a magnetic field B is created, the velocity of electron ω will be given by the equation|
|45. ||If v is the velocity of electron, tc is the average time between collisions, the mean free path λ = vtc.|
|46. ||Assertion (A): An electron having charge – e and mass m and lying in an electric field E is subjected to an acceleration – (e/m) E.|
Reason (R): If there are n electrons/m3 moving with velocity vx and each electron has a charge – e, the current density J = – n evx.
|A.||Both A and R are true and R is correct explanation of A|
|B.||Both A and R are true but R is not correct explanation of A|
|C.||A is true but R is false|
|D.||A is false but R is true|
|47. ||When a pentavalent impurity is added, the semiconductor becomes|
|48. ||In body centred cubic structure, comers and centre of the cube are occupied by identical atoms.|
|49. ||For a multiplate capacitor having n plates, A as area of each plate, the capacitance is proportional to|
|B.||(n – 1) A|
|C.||(n + 1) A|
Answer: Option B
If the number of plates is n, the number of capacitors is (n – 1).
|50. ||The orientation polarization is|
- directly proportional to temperature
- inversely proportional to temperature
- inversely proportional to square of permanent dipole moment
- directly proportional to square of permanent dipole moment.
Which of the above are correct?
|A.||1 and 3 only|
|B.||2 and 3 only|
|C.||1 and 4 only|
|D.||2 and 4 only|