Physics 106, Summer 2012

Reading: Chapter 18 Sec 1-4

Did you complete the reading assignment?

Yes No

Did you complete the entire quiz or spend at least 15 minutes working on this quiz and the attached links? Yes No

1) Resistance is a measure of its opposition to the passage of a steady electric current.

2) Current is the flow of electric charge.

3) Voltage, resistance, and current are related to each other through Ohm's Law.

The last quiz talked about capacitance and how charge can be stored. In order for this to happen charge has to move. This is called current. The more charges moving and the higher the speed at which they move, the higher the current. Resistance is what slows down or decreases the current.

Conventional current is the flow of positive charge in a circuit. What flows through an electrical circuit?

Protons Electrons Both protons and electrons

Exercise 1

Try this link: http://www.mste.uiuc.edu/murphy/Resistance/default.html Increase and decrease the values of voltage and resistance and observe what happens. Think of a traffic jam, and how the applet reminds you of a traffic jam.

What is the current like?

The number of cars on the road. How fast the cars are moving on the road. How many cars get through a certain stretch of road in a certain amount of time. The number of lanes the cars can travel in stretch of road at a given time.

What is the resistance like?

The number of cars on the road. How fast the cars are moving on the road. How many cars get through a certain. The number of lanes the cars can travel in stretch of road at a given time.

What is the voltage like?

What happens when the resistance is increased greatly?

The charges pile up at the source of resistance and move through very slowly, like cars when a four lane highway merges into a one lane highway.

Exercise 2

Go to the following applet and click the 'Run Now' button: http://phet.colorado.edu/simulations/sims.php?sim=Ohms_Law

Increase and decrease the voltage and resistance of the simple circuit using the sliders at the top right. You will see values for voltage, resistance, and current as well as watching the size of the variables in the equation change size and the size of the arrows increase or decrease to help you see relative values.

As you increase voltage, what happens to the current?

It increases It decreases

As you increase resistance, what happens to the current?

Why does current flow in a circuit?

There is an electric potential from one end of the batter to the other. Electrons will flow through the circuit as a result of this potential difference.

The pendulum in pendulum court has a warning on it that reads: "Warning: 10,000 Ohms". Should this warning scare you from touching the pendulum? Why or Why not?

No, ohms are a measurement of resistance, which cannot hurt you because it is impeding the flow of current. A better warning sign might say "If you touch this pendulum, we will force you to change your major to physics."

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Was there anything that you didn't understand in the reading assignment? What was confusing to you?

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