NEET UG - Electric current, drift velocity, mobility and relation with current, Ohms law One Line Questions & Answers

1. A copper wire has a cross-sectional area of 1 mm². If the electron density in copper is 8.5 x 10²⁸ m⁻³, and the drift velocity is 0.5 mm/s, what is the current flowing through the wire? (Elementary charge e = 1.6 x 10⁻¹⁹ C) — 0.68 A

2. The drift velocity of electrons in a metal is typically of the order of: — 10⁻⁴ m/s

3. A conductor carries a current of 2 Amperes. What is the amount of charge passing through a cross-section of the conductor in 5 seconds? — 10 Coulombs

4. A battery supplies a constant voltage of 12V to a resistor. If the resistance is 3 Ohms, what is the current? — 4 A

5. A wire carries a current of 1 A. If the electron density is 10²⁹ m⁻³ and the area of cross-section is 1 mm², what is the drift velocity of electrons? (e = 1.6 x 10⁻¹⁹ C) — 6.25 x 10⁻⁴ m/s

6. What is the unit of current density (J)? — A/m²

7. For a material that does not obey Ohm's law (non-ohmic), the V-I graph is: — A curve

8. Which factor does NOT affect the drift velocity of electrons in a conductor, assuming Ohm's law is obeyed? — The color of the conductor

9. In Ohm's Law, the constant of proportionality between voltage (V) and current (I) is: — Resistance

10. Which physical quantity is represented by the slope of the V-I graph for an ohmic conductor? — Resistance

11. If the number of free electrons per unit volume (n) in a conductor increases, and other factors remain constant, the current for a given drift velocity will: — Increase

12. A constant voltage is applied across a resistor. If the resistance of the resistor is decreased, the current flowing through it will: — Increase

13. If the temperature of a metallic conductor increases, its resistance: — Increases

14. Mobility (μ) of charge carriers is defined as the ratio of: — Drift velocity to electric field

15. Consider a conductor of length L and cross-sectional area A. If a voltage V is applied across its ends, the electric field E inside the conductor is approximately: — E = V / L

16. Which of the following quantities is NOT a vector? — Electric current

17. Electric current is defined as the rate of flow of: — Electric charge

18. The charge carriers in metals are: — Electrons

19. In the equation J = σE, if the electric field E is doubled, the current density J becomes: — Double

20. If the voltage across a resistor is doubled, and the resistance remains constant, the current through the resistor will: — Double

21. If the length of a conductor is doubled while keeping the cross-sectional area and applied voltage constant, the drift velocity of electrons will: — Remain the same

22. If the conductivity of a material is high, its resistivity is: — Low

23. If the current density (J) in a conductor is uniform and the area of cross-section is A, the total current I is given by: — I = J A

24. Which of the following correctly relates electric current (I), drift velocity (v_d), charge carrier density (n), charge of carrier (q), and area of cross-section (A)? — I = n A v_d q

25. Which of the following represents the mathematical definition of electric current (I)? — I = Q/t

26. What is the direction of drift velocity of electrons in a conductor when an electric field is applied? — Opposite to the direction of the electric field

27. If the relaxation time (τ) of electrons in a conductor decreases, the drift velocity for a given electric field will: — Decrease

28. If the temperature of a semiconductor increases, its resistance: — Decreases

29. What happens to the drift velocity of electrons in a wire if its cross-sectional area is increased, while the current remains the same? — It decreases

30. If a material has very high electron mobility, it implies that: — Electrons can drift easily under a small electric field

31. Which of the following statements is INCORRECT regarding drift velocity? — It is independent of the temperature of the conductor.

32. Which statement best describes the microscopic form of Ohm's law? — J = σ E, where J is current density, σ is conductivity, and E is electric field.

33. The relation I = n A v_d q can be rewritten using v_d = μE and E = V/L as I = n A μ q (V/L). This implies that the resistance R is proportional to: — L / (n A μ q)

34. The SI unit of mobility is: — m/(V·s)

35. The resistance of a wire depends on: — Material, length, and area of cross-section

36. Ohm's law is not valid for: — All of the above

37. The charge carriers in semiconductors (like Silicon) are: — Electrons and holes

38. If a resistor obeys Ohm's law, its V-I graph is a: — Straight line passing through the origin

39. If two resistors R₁ and R₂ are connected in series, the equivalent resistance is: — R₁ + R₂

40. If two resistors R₁ and R₂ are connected in parallel, the equivalent resistance is: — R₁ R₂ / (R₁ + R₂)

41. The average time between successive collisions of electrons with the lattice ions in a conductor is called: — Relaxation time (τ)

42. Conductivity (σ) is the reciprocal of: — Resistivity (ρ)

43. Drift velocity is defined as: — The average velocity with which free electrons get drifted under the influence of an external electric field.

44. What is Ohm's Law? — The current through a conductor is directly proportional to the voltage across its ends, provided temperature and other physical conditions remain unchanged.

45. The drift velocity (v_d) of charge carriers in a conductor is proportional to: —

46. Drift velocity is directly proportional to relaxation time (τ) and electric field (E). The relation is: — v_d = e E τ / m

47. The relationship between drift velocity (v_d) and electric field (E) is given by: — v_d = μ E

48. What is the SI unit of electric current? — Ampere

49. Ohm's law is fundamentally a statement about the relationship between: — Electric field and current density

50. What is the definition of mobility (μ) in terms of drift velocity (v_d) and electric field (E)? — μ = v_d / E

Electric current, drift velocity, mobility and relation with current, Ohms law - One Line Questions