TUCSON, ARIZ., Jan. 31-Teri Volpin returned to jail here on Friday after a Federal judge found her guilty of contempt for her second refusal to answer broad questions about her activities before a Federal grand jury in Tuscon.

The grand jury is investigating an alleged Weatherman plot to purchase explosives in Tucson and transport them to California.

Volpin was sentenced to remain in jail until the end of the grand jury term. The jury is scheduled to adjourn on March 31, but the Justice Depart-ment will probably extend the term until December 31.

Volpin had been released from jail last Wednesday, after she had served a sixty day sentence she received for refusing to testify before the grand jury in November. Immediately after her release, she received a subpoena ordering her to reappear Thursday before the grand jury. She appeared on Thursday, but again refused to testify.

Volpin is one of 5 people from Venice, Calif. who have been convicted of contempt for refusing to answer questions before the Tuscon grand jury. The others are still serving their first contempt sentence.

In appearances before the grand jury, the five have been asked to describe all "demonstrations and riots" in which they took part last year, all trips they made outside the state of California, and some they made inside the state, all discussions they had during the last year with a large number of individuals, and all discussions that took place in their homes.

The five have continued to refuse to testify on the grounds that the questions violate their rights under the First, Fourth, Fifth, Sixth, and Ninth Amendments, and on the grounds that the questions are vague and irrelevant to the grand jury's official purpose, to investigate the alleged plot to transport explosives.