Questions: If an electron is accelerated from rest through a potential difference of 1,500 V, what speed does it reach?
2.3 × 10^7 m / s
1.9 × 10^7 m / s
1.5 × 10^7 m / s
1.1 × 10^7 m / s
Transcript text: If an electron is accelerated from rest through a potential difference of $1,500 \mathrm{~V}$, what speed does it reach?
$2.3 \times 10^{7} \mathrm{~m} / \mathrm{s}$
$1.9 \times 10^{7} \mathrm{~m} / \mathrm{s}$
$1.5 \times 10^{7} \mathrm{~m} / \mathrm{s}$
$1.1 \times 10^{7} \mathrm{~m} / \mathrm{s}$
Solution
Solution Steps
Step 1: Determine the Energy Gained by the Electron
The energy gained by an electron when it is accelerated through a potential difference \( V \) is given by the equation \( E = eV \), where \( e \) is the charge of the electron (\(1.6 \times 10^{-19} \, \text{C}\)) and \( V \) is the potential difference.
For a potential difference of \( 1,500 \, \text{V} \), the energy gained is \( E = 1.6 \times 10^{-19} \, \text{C} \times 1,500 \, \text{V} \).
Step 2: Relate Energy to Kinetic Energy
The energy gained by the electron is converted into kinetic energy, which is given by the equation \( \frac{1}{2}mv^2 \), where \( m \) is the mass of the electron (\(9.11 \times 10^{-31} \, \text{kg}\)) and \( v \) is the speed of the electron.
Set the kinetic energy equal to the energy gained: \( \frac{1}{2}mv^2 = eV \).
Step 3: Solve for the Speed of the Electron
Rearrange the equation to solve for \( v \): \( v = \sqrt{\frac{2eV}{m}} \).
Substitute the known values: \( v = \sqrt{\frac{2 \times 1.6 \times 10^{-19} \, \text{C} \times 1,500 \, \text{V}}{9.11 \times 10^{-31} \, \text{kg}}} \).
Calculate \( v \) to find the speed of the electron.