Question

1) When charges pass through a resistor, they give up kinetic energy to the environment in the form of heat. Consider a circuit in which the wires on either side of a resistor are exactly the same diameter. The average drift speed for charges entering the circuit is venter. The drift speed for charge exiting the resistor is vexit. Is vexit greater than, less than, or equal to venter

Answer 1

$\frac{1}{2}$Answer:

    $v_{exit } < v_{enter}$

Explanation:

To propose the solution of this problem we must use the relationship between work and energy

         W = ΔK

the change in kinetic energy is

         ΔK = K_f -K₀

         ΔK = ½ m v_f² - ½ m v₀² = ½ m (v_f² - v₀²)

in this case

         ΔK =  $\frac{1}{2} m ( v_{exit}^2 - v_{enter}^2 )$

we can find work with the first law of thermodynamics

         $\Delta E_{int}$ = Q + W

where \Delta E_{int} is the internal energy of the body, usually measured in the form of an increase in the temperature of the system

          W = \Delta E_{int} - Q

if we consider that the internal energy does not change

         W = -Q

we substitute everything in the first equation

        -Q =   $\frac{1}{2} m ( v_{exit}^2 - v_{enter}^2 )$

Because they are squared, the variables are positive, therefore, for the equation to be fulfilled, the exit velocity must be less than the entrance velocity.

            $v_{exit } < v_{enter}$