Now Ezra moves the same two batteries into a flashlight and switches it on.

Electricity carries energy from the batteries to the bulb. The bulb shines, and the bulb gets warm.

The flashlight's energy chain: electricity carries energy to the bulb; the light carries energy on to the wall, and the warm bulb has a little thermal energy.

The light carries energy out of the flashlight, onto the wall. The warm bulb has a little thermal energy.

Now Ezra moves the same two batteries into a hand warmer. The pack warms up, so the pack has thermal energy.

The hand warmer's energy chain: electricity carries energy from the batteries to the pack, and the warm pack has thermal energy.