D.C. voters will go to the polls Tuesday to elect a member to fill the at-large City Council seat left vacant by the death of Julius Hobson March 23.

All of the District's 222,274 registered voters are eligible to vote in this election in which 10 candidates seek the remaining 18 months of Hobson's term. That term expires in 1978. The candidate getting the most votes ill win the election.

Democrats cannot run in this election, although they can vote, because the Home Rule charter stipulates that only two of the four at-large City Council seats can be held by any one party. Democrats now hold two at-large seats.

Polls open at 7 a.m. and close at 8 p.m. Voters in 20 precincts of ward three will be using the Gyrex voters' penciled-in choices on long paper ballots. All voters will use the same ballots, but only those in ward three will use the Gyrex machines.

Election officials said the machines are used in different wards in each election to acquaint voters and precinct workers with the machines.

Paper ballots will be collected from those wards not using the Gyrex machines and will be tallied at the Martin Luther King Library election central. For further voting information, call 347-9725 or 785-2619.