Electricity Lab Part 2

We started working with electricity recently and have used inquiry to discover Ohm's Law ( V = IR ). We are going to use Ohm's Law to help us make sense of a strange phenomenon. Electric circuits seem to have a mind of their own. In fact, the way in which you connect the same objects in a circuit can have a dramatic effect. We are going to use Phet's DC Circuit Construction Simulation to explore a number of circuits. You are going to explore 5 circuits in total. For each circuit you must record in your notebook:

• Voltage of the battery
• Current through the circuit
• Resistance of the light bulb (make sure each bulb has the same resistance)
• A diagram of what the circuit looks like
• Voltage drop across each light bulb

Follow this first video to help you get your first circuit set up. You may choose any battery voltage (stay low enough to keep from blowing the circuit) and any resistance for the light bulbs (keep it low enough that the lights turn on).

In the first video the "voltage drop" across the light bulb was 12 v. Think of a completing a circuit like completing a log flume, at the end you are at the same height that you started. If the battery brought the voltage up by 12 v then we have to go back down 12 v before we get back. But how does this change when you have multiple light bulbs. Build the circuit in the second video to find out.

We have seen a series circuit before. It makes sense to think that adding multiple light bulbs to the same battery will make them dimmer because there is less energy to go around. But what if I told you that adding more light bulbs would actually make each bulb brighter? Seems crazy doesn't it? Try out the circuit in the third video.

There are an infinite number of ways to create circuits. Try building the last two circuits in the fourth video. Each combine a portion of a series circuit and portion of a parallel circuit. Don't forget to measure the voltage drop across each bulb on each circuit!

When Lightning Strikes

We have all have seen lighting at different times in our life, but what is it? What causes it? How dangerous is it?

Lets look at what lightning is first. A flash of lightning is simply an exchange of charged particles (electrons) between a cloud and the planet. In fact, this is no different than when you get a little shock on a doorknob after dragging your feet along a carpet. Friction between objects often results in stripping electrons from one material and adding them to another. This can cause things to build up a charge. Objects like to be electrically neutral, so when there is an opportunity to dump excess charge into the earth (basically an infinitely large neutral object) the charge will jump in a flash.

While we collect a charge by rubbing our rubber shoes along carpet, clouds accumulate their charge because of colliding ice particles and water droplets. These collisions knock electrons around and cause a polarization as positively charged molecules continue to rise through the cloud. Once enough negative charge accumulates at the bottom of the cloud the Earth starts to feel the effect.Things on the ground begin to have electrons pushed further way from the cloud, leaving positively charged objects on the surface. Eventually, the charge balances out by jumping across the insulating air and bridging the connection to the ground with the tallest available object.


Lightning may be incredible to watch but it is still extremely dangerous. A single bolt can contain roughly the same amount of energy as 500 sticks of dynamite! In fact lightning is responsible for about 1000 deaths every year, and many more very serious injuries. The best thing to do when you hear or see lightning is to get indoors, away from metal, and low to the ground. If you can get to one of these vantage points then feel free to sit back and enjoy the show! Whether you are checking out upward lighting, volcanic lightning, or cloud to cloud lightning.