An external force in assembling this configuration of charges B.3ke2/2a.Therefore ,B. –3ke2/2a is correct .
To determine the work done by an external force in assembling this configuration of charges, we need to calculate the potential energy of the system. The potential energy of a system of charges is the amount of work required to bring the charges together from an infinite separation.
In this case, we have two protons (each with a charge of +e) and one electron (with a charge of -e) arranged along a line. The distance between the electron and each proton is a.
The potential energy of the system can be calculated using the following formula:
U = ke^2/r
where:
U is the potential energy
k is Coulomb's constant (8.99 x 10^9 N m^2/C^2)
e is the elementary charge (1.60 x 10^-19 C)
r is the distance between the charges
The total potential energy of the system is the sum of the potential energies of each pair of charges. Therefore, we have:
UE = U(electron, proton 1) + U(electron, proton 2) - U(proton 1, proton 2)
Plugging in the values, we get:
UE = (-ke^2/a) + (-ke^2/a) + (ke^2/2a)
Simplifying, we get:
UE = -3ke^2/2a
Therefore, the work done by an external force in assembling this configuration of charges is -3ke^2/2a. This means that the external force had to do work against the repulsive forces between the charges to bring them together.
Question
Two protons and an electron are assembled along a line as shown above. The distance between the electron and each proton is a. What is the work done by an external force in assembling this configuration of charges? A –2ke2/a B –3ke2/2a C ke2/2a D 3ke2/2a E 3ke2/a .