Question

XCO DE Problems 1-3 are based on the following description Electrical energy is applied to a system enclosed inside the piston-cylinder device shown below. The voltage is 10 volts and the current is 2 amps for 20 seconds. During this time there is a heat transfer from the system to the outside equal to 90J, the system expands 0.2 m at a constant pressure of 200 kPa. The amount of electrical energy in J applied to the system is closer to: 200 0.4 250 600 400 2000 4100 Question 2 1 pts

Answer 1

Given: I = 2 amps ; V= 10 volts; Time(t) =20 sec ; P= 200 KPa= constant; dv= 0.2$m^{3}$ ;Q= -90 J

(1)The amount of electric energy applied to the system is given by:

Weles V*I*t= 10 * 2 * 20 = 400J

(2)The expansion work is:

(3)The increase in energy of system(dE):

From 1st law of thermodynamics:

$dQ=dE+dW$

$Q=dE+W_{exp}-W_{elec}$ ( since the electrical energy is applied to the system so it is taken as negative and the expansion is done by the system so it is taken as positive)

=> -90=dE+40000-400

so, dE= -39690 J

Note: ques (2) and (3) option doesn't match because something wrong with the data given in ques.