Electric current, drift velocity and mobility - One Line Questions
1.
A current of 1 A flows through a wire. If the cross-sectional area is 1 mm^2 and the number density of electrons is 10^29 m^-3, calculate the drift velocity. —
10^-5 m/s
2.
If a conductor carries a current of 0.5 A, and the drift velocity of electrons is 2.5 x 10^-4 m/s, what is the effective cross-sectional area if the electron density is 10^28 m^-3? —
10^-6 m^2
3.
A conductor has a current of 1.6 A. If the charge of an electron is 1.6 x 10^-19 C, how many electrons pass through a cross-section per second? —
10^19
4.
If a charge of 10 Coulombs passes through a conductor in 2 seconds, what is the current? —
5 Amperes
5.
The mobility of electrons in copper is approximately 4.3 x 10^-3 m^2 V^-1 s^-1. If an electric field of 10^-2 V/m is applied, what is the drift velocity? —
4.3 x 10^-5 m/s
6.
Drift velocity is a consequence of the interaction between charge carriers and the: —
Both A and B
7.
The drift velocity of charge carriers in a conductor is directly proportional to the product of relaxation time and: —
Electric field strength
8.
Mobility is defined as the magnitude of drift velocity per unit: —
Electric field
9.
If the relaxation time of electrons in a conductor increases, the drift velocity will: —
Increase
10.
If the length of a conductor is doubled while keeping the voltage across it constant, the electric field strength: —
Halves
11.
Which of the following quantities is a vector? —
Drift velocity
12.
Mobility of charge carriers is a property of the: —
Material of the conductor
13.
In the formula I = n A v_d e, 'e' represents: —
Charge of an electron
14.
In a metallic conductor, the charge carriers responsible for electric current are: —
Electrons
15.
The direction of conventional current is defined as the direction of flow of: —
Positive charge
16.
In a semiconductor, the charge carriers can be both electrons and holes. Their mobility values are generally: —
Different
17.
If the drift velocity of electrons in a conductor doubles, and other factors remain constant, the current will: —
Double
18.
Mobility of charge carriers in semiconductors is generally: —
Lower than in metals
19.
The relationship between current (I), drift velocity (v_d), charge carrier density (n), and cross-sectional area (A) is given by: —
I = n A v_d e
20.
The relationship between drift velocity (v_d) and current (I) for a conductor of cross-sectional area A is: —
I ∝ v_d
21.
If the number density of charge carriers (n) in a conductor decreases, and drift velocity remains the same, the current will: —
Decrease
22.
In a conductor, the collisions of electrons with the lattice ions cause: —
Both B and C
23.
As temperature increases, the drift velocity of electrons in a conductor generally: —
Decreases
24.
What happens to the drift velocity if the cross-sectional area of the conductor decreases, while current and charge carrier density remain constant? —
Remains the same
25.
Which of the following statements about drift velocity is true? —
It is the net velocity of electrons in the direction of the electric field.
26.
Which statement is INCORRECT regarding electric current? —
It is defined as the rate of flow of protons.
27.
If the number of free electrons per unit volume in a conductor is 'n', the current density (J) is given by: —
J = n e v_d
28.
In a conductor, the mean free path of electrons is related to relaxation time and their average speed. A shorter mean free path implies: —
Shorter relaxation time
29.
The SI unit of mobility is: —
m^2 V^-1 s^-1
30.
Which of the following is NOT a factor determining mobility? —
Electric field strength
31.
In the equation v_d = e E τ / m, 'm' represents: —
Mass of the electron
32.
Which of the following has higher mobility of charge carriers? —
Metals
33.
When an electric field is applied across a conductor, the free electrons: —
Drift in a direction opposite to the electric field
34.
In most metallic conductors, the drift velocity of electrons is in the direction: —
Opposite to the applied electric field
35.
Electric current is defined as the rate of flow of: —
Electric charge
36.
The average time interval between two successive collisions of electrons in a conductor is called: —
Relaxation time
37.
Which quantity is directly proportional to the electric current passing through a conductor? —
Drift velocity
38.
Which material typically exhibits the highest mobility for its charge carriers? —
Copper
39.
Mobility is a measure of how easily charge carriers can move under the influence of an electric field. Higher mobility means: —
Faster movement of charge carriers
40.
Which of the following factors affects the drift velocity of electrons in a conductor? —
All of the above
41.
The relaxation time (τ) is inversely proportional to: —
Temperature
42.
Ohm's law relates voltage, current, and resistance. It is a consequence of the microscopic description involving drift velocity when: —
The electric field is uniform and temperature is constant
43.
If the temperature of a metallic conductor increases, the resistance increases because: —
The relaxation time of electrons decreases
44.
What is drift velocity? —
The average velocity of charge carriers in a specific direction under an electric field
45.
Mobility of charge carriers is defined as: —
The ratio of drift velocity to electric field strength
46.
Consider a wire of length L and cross-sectional area A. If a voltage V is applied across its ends, the electric field E is approximately V/L. The drift velocity is proportional to: —
V/L
47.
Drift velocity (v_d) is related to relaxation time (τ) and electric field (E) by the equation: —
v_d = e E τ / m
48.
The drift velocity is directly proportional to the applied electric field (E) and the mobility (μ). This relationship is expressed as: —
v_d = μ E
49.
The drift velocity of electrons in a conductor is generally: —
Very low, of the order of 10^-4 m/s
50.
What is the SI unit of electric current? —
Ampere