Jars of thick purple jam. Wedges of creamy-looking pies. Shelf upon shelf of pickels and preserves, biscuits and breads.

It's the Home Arts Building at this year's Montgomery County Fair, in progress through Saturday a the fairgrounds in Gaithersburg. As tractors, carnival rides and thousands of voices provide the background music outside, anxious exhibitors quietly wander through the building, looking for their entries.

Then a shout: "Hey, I got a second place on my beets!"

There are approximately 5,300 exhibitors at this year's fair, and more then 15,000 entries, ranging from cabbages to dairy cattle to embroidered neckties.

Russ and Jean Brungard were checking the floral entries to see how their daughter Karen, 10, had fared with her marigolds.

"She entered four flowers and has three ribbons," Jean Brungard noted proundly. She and her husband exhibited vegtables from their garden, and capped a first prize for their endive.

"Once you start entering, you really get hooked," said her husband. "It's such a rewarding feeling to dash into the building and find a ribbon on something you grew."

Nearly, Thelma Fletcher of Gaithersburg had to use the official rule book to check her results. That's because she entered more than 100 pies, canned goods and preserves in competition.

"I came home from work last Friday and put up my canned stuff until 3 a.m.," she explained, laughing. "I got up two hours later to do some more. Then I rushed it all over to the fair and came home to start baking."

Hundreds of thousands of visitors in the next few days are expected to browse past the farm displays, test their skills at carnival booths, sample the food and socialize.

David Goody, 14, and his 15-year-old sister Jennifer will be at the fair every day this week, but they don't plan to stray far from the 4-H Beef Club exhibit.

Six steers they on the family's six acres in Brookville are in the barn with them.

"We picked them out, bought them and raised them," said David. "Then we brought them to the fair. They'll compete and then we'll sell 'em."

The youngsters don't seem to mind that their charges will soon become hamburger.

"We don't name them," explained Jennifer. "I'm not attached to them. It's even a little hard to tell them apart."

Each night the cattle are tied up outdoors, and David and the other 4-H boys sleep in the barn.

"I'm here all day," said David, sitting on an orange canvas chair near one of the his steers. "We all feel like we have to be."

For hundreds of the county's 4-H members, the fair is the highlight of the year's activities. Besides entering their projects in competition, they made floats and marched in a parade Monday night.

Terry Suddath, a Damascus High senior, was chosen 1980 4-H Queen. Special events in the next few days include a tractor-pull contest tonight at 7, the 4-H swine sale tomorrow at 7 p.m. and the steer sale at 8, and entertainment. The Country Currents perform tomorrow night at 7:30 and the Carter Family is billed for Saturday night at 7.

Admission is $3 for adults and $1 for children. Parking costs an additional $1. To get to the fair, take I-270 to the Gaithersburg exit and follow the signs.