Current and Drift Velocity Relation

Q.

Define the drift velocity of electrons in a conductor?

Q. We know that current $I=neA{V}_d$ where $V_d$ is the drift speed, A is the cross sectional area, e is the magnitude of charge on an electron and n is the number of free charge carriers in unit volume of a conductor. In a conductor of non-uniform cross-sectional area as shown

1: The current at P will be more than the current at Q
2: Because current is directly proportional to cross-sectional area so current increases as the cross sectional area increases

1. Statement 1 is correct, Statement 2 is the correct and Statement 2 is the correct explanation for statement 1
2. Statement 1 is correct, Statement 2 is the correct and Statement 2 is not the correct explanation of statement 1
3. Statement 1 is correct but Statement 2 is wrong
4. Both statements are wrong

Q. A wire has a non-uniform cross-sectional area as shown in figure. A steady current i flows through it. Which one of the following statement is correct

1. The drift speed of electron is constant
2. The drift speed increases on moving from A to B
3. The drift speed decreases on moving from A to B
4. The drift speed varies randomly

Q. Consider a conductor of variable cross section in which current is flowing from cross section ‘1’ to ‘2’. Then which of the following is/are correct?

1. Current passing through both the cross sections is same
2. Current through ‘1’ is less than that through ‘2’
3. Drift velocity of electrons at ‘1’ is less than that at ‘2’
4. Drift velocity is same at both the cross sections.

Q. An electron beam has an aperture $1.0{\text{mm}}^2$. A total of $6.0\times {10}^{16}$ electrons go through any perpendicular cross-section per second. Find $\left(a\right)$ the current and $\left(b\right)$ the current density in the beam.

1. $6.3\times {10}^{-3}\text{A}\&6.3\times {10}^3{\text{A/m}}^2$
2. $3.2\times {10}^{-3}\text{A}\&3.2\times {10}^3{\text{A/m}}^2$
3. $9.6\times {10}^3\text{A}\&9.6\times {10}^{-3}{\text{A/m}}^2$
4. $9.6\times {10}^{-3}\text{A}\&9.6\times {10}^3{\text{A/m}}^2$

Q. Two wires each of radius of cross-section $r$ but of different materials are connected together end to end (in series). If the densities of charge carriers in the two wires are in the ratio $1:4$, the drift velocity of electrons in the two wires will be in the ratio

Q. A wire has a non-uniform cross-sectional area as shown in figure. A steady current i flows through it. Which one of the following statement is correct

1. The drift speed of electron is constant
2. The drift speed increases on moving from A to B
3. The drift speed decreases on moving from A to B
4. The drift speed varies randomly