When making the /v/ sound, the lower lip moves up and does not touch the lower teeth. The /v/ sound is voiced, which means that we use our vocal chords to make it. If you place your hand on your throat when making the /v/ sound you will feel a vibration.
When making the /b/ sound, the lips come together and then open when the air is released. The /b/ sound is also voiced.
Read these words to your student(s) and have them repeat.
For more pronunciation exercises, come in to pick up a copy of Pronunciation Fun! (Free for IC teachers and students.)