Unit 3, Chapter 8

Integrated Science

Unit Three: Electricity and Magnetism

8.1 Ohm's Law

8.2 Work, Energy, and Power

Chapter 8 Electrical Relationships

Chapter 8 Learning Goals Measure how current changes when voltage is increased. Measure how current changes when resistance is increased. Describe how voltage, current, and resistance are related. Use Ohm’s law to solve circuit problems. Explain why resistors are used in a circuit. Define power as the rate at which energy flows. Describe relationships between work, energy, and power. Calculate power use in a circuit. Rank the amount of power used by various household appliances. Estimate the cost per month of using a common household

appliance. Use dimensional analysis to find out what we buy from electric

utility companies. Explain how to choose a safe extension cord.

Chapter 8 Vocabulary Terms

horsepower

kilowatt

kilowatt-hour

Ohm’s law

potentiometer

power

resistor

watt

8.1 Ohm's Law

Key Question:

How are voltage, current and resistance related?

*Read text section 8.1

AFTER Investigation 8.1

8.1 Using Ohm's Law

German physicist Georg Ohm experimented with circuits to find an exact mathematical relationship between voltage, current and resistance.

Ohm's law can be used to predict any one of the three variable if given the other two.

8.1 Graphing and Ohm's law

8.1 Resistors

Electrical components called resistors can be used to control current.

Resistors have striped color codes to record their "values" (writing on them is difficult).

8.1 Electrical controls Potentiometers are a type of "variable" resistor that can

change from low to high.

They are wired so that as you turn the knob, it changes the distance the current has to flow.

8.2 Work, Energy, and Power

Key Question:

How much does it cost to use the electrical appliances in your home?

*Read text section 8.2 AFTER Investigation 8.2

8.2 Electric Power

Power is the rate at which energy flows.

Electric companies charge a rate for the energy you use.

We use "watts" as a standard unit because energy can be converted into many different forms.

8.2 Electrical Power

P = VIcurrent (amps)

voltage (volts)

Power (watts)

8.2 Electricity, power, and heat