On Jan. 10, about 250 Philadelphia area high school students filled a lecture hall to watch the 20th Annual Physics Demonstration Show at the University of Pennsylvania. It was the third of four two-hour presentations, each one packing the lecture hall almost to capacity for a total of nearly 1,000 students, a step up from attendance of the last few years.

Bill Berner, Penn’s demo lab coordinator, stood at the front of the lecture hall with an eclectic collection of instruments and objects, ranging from balloons to a Van de Graaff generator, all part of his tool kit to show off the laws of electricity and magnetism. Each year, Berner cycles through demonstrations of different topics, including mechanics, light and waves. This year’s topic was electricity and magnetism.​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​Berner came to Penn about 20 years ago to do undergraduate lab setups, but his sights were set on putting together physics demonstrations. He slowly worked his way into his current position. Prior to that, he had spent 25 years teaching in a high school in Springfield, Pa.

“The minute I got in here I was stunned to find out how much of the stuff that I was reading about in national and international publications was happening 10 miles from where I was teaching and I didn't know it,” Berner said. “I thought ‘This is nuts. This needs a wider audience.’”​​​​​​​

And so in 1997 the annual Physics Demonstration Show was born.

​​​​​​​“I realized that this was the stuff that would have really enhanced what I was trying to teach,” Berner said. “High school students are concrete thinkers, and throwing equations on the board is not advancing the cause. What you need to do is show them an event that has an unexpected outcome and force them to reassess the way they think about it.”​​​​​​​At first, Berner said, he was “in the dark,” unsure of whether Penn was happy to have a thousand high school kids pouring through its lobby. But after a few years he was nominated for a Models of Excellence award by the department.

“That really put a lot of wind in my sails,” Berner said. “It was really gratifying to see the extent to which Penn is ready to support and, in fact, encourage outreach work. And that has continued for all 20 years that I've been here.”​​​​​​​​​​​​​​Physics is one of the more challenging teaching tasks, Berner said. But on the flip side, there are more “aha” moments in introductory physics than in any other teaching arena.

“If you're really a teacher then that's probably what motivates you,” he said. “That look in the eyes of your class when suddenly you've shown them something that they realize is worth knowing. It's really neat to trigger something that, hopefully, has some lasting value.”

One way to overcome the challenges of teaching physics, in particular electricity and magnetism, is to get the forces and behaviors big enough to be macroscopic, he said.

“There are ways of getting invisible things to be visible.”

This year’s show literally ended in a bang: Berner exploded a small model house during his demonstrations of lightning. He stressed that incorporating some theater into what you do is an important part of being a teacher.​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​“You need to have something that gets out of short-term memory, and blowing up a house up gets us into longer-term memory,” he said. “So now that we've established a beachhead, what can we glom onto that memory.”   

Berner’s favorite demos involve discordant events, counterintuitive issues that go beyond the basic. In one part, he allowed himself to get shocked by a 4-inch spark from the Van de Graaff generator and came out unscathed.​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​He said that this demonstrates one of the big issues with electricity, which is people using the words voltage and current interchangeably.​​​​​​​

“So now we've got to come to grips with this,” he said. “The reason that this isn't a problem is that we've got lots of voltage and not much current. If I reverse that then we might have a different circumstance.”

Berner believes that in the United States there's not a full appreciation of science as “a way of knowing.” He hopes that these demonstrations might help overcome this issue.“I think, especially at the introductory level, using demonstrations correctly is a tremendously helpful way to say, ‘This stuff that I'm telling you here has a very strong basis. People have been checking on this repeatedly for the last two centuries, and they can't get it to be wrong, so we're going use this information,’” he said. “So that's why this lab is worth keeping.”