Question

A system consists of a gas inside a cylinder. Inside the cylinder there is a 10 ohm resistor connected to an electrical circuit through which a current can pass. A mass of 0.1kg is placed on the piston which drops by 0.2 m and comes to rest. A current of 0.1 A is passed through the 10 ohm resistor for 2s. What is the change in the internal energy of the system when it has reached equilibrium?

Answer 1

The mass performs work and it value is equal to

$$W=mgh (1)$$

Using (1) we got: W = 0.196 J

On the resistor, heat is released and and it value is equal to

$$Q=I^2Rt (2)$$

Using (2) we got: Q = 0.2 J

The change in the internal energy of the system is equal to

$$W+Q (3)$$

We got 0.396 J

Answer:

0.396 J