A small but measurable current of 5.8 × 10-10 A exists in a copper wire whose diameter is 3.0 mm. The number of charge carriers per unit volume is 8.49 × 1028 m-3. Assuming the current is uniform, calculate the (a) current density and (b) electron drift speed.

a) J = 8.2×10^-5A/m^2

b) V = 6.07×10^-15m/s

Explanation:

The current density is the ratio of current to area of the wire.

J = i/A

Drift speed is inversly proportional to the square of the radius of the wire.v α 1/r^2

Please find the attached file for the solution

answer: option c. i.e. electric current flowing “downhill” from the negative electrode to the positive electrode in a battery

explanation:

the water analogy to the circuits define the pipes (water flows) to the electric current. now, we know that the electric current flows from the positive terminal to the circuit (as shown in the diagram attached).

hence, option c is the correct answer.