Chapter 13Electricity!

Quick review:

ConductorsInsulatorsLike charges ___________ and unlike

charges _____________.

Repel

Attract

An objects electric charge depends on the imbalance of it protons and electrons.

Objects can be charged by the transfer of electrons.

Charging by Friction, Conduction and ________________.

Electric Force = the force of attraction or repulsion between object due to charge.

Electric Force depends on charge and _______________.

Voltage and Current!

Volt is the SI unit for potential difference. (voltage) (V)

A cell is a source of electrical current because of the potential difference, or voltage, between the terminals.

A voltage sets a charge in motion. Example: Electrons move from the negative

terminal of a battery to the positive terminal when a flash is turned on.

Current is the rate that electric charges move through a conductor.Measured in Amperes (A)SI unit I

*Conductors have low resistance*

Resistance is the ratio of voltage across a conductor to the current it carries.

Resistance is caused by internal friction and slows the movement of charges.

Resistance = Voltage/Current

Practice problemsThe heating element in an electric kettle

has a resistance of 30 Ω.

What is the current in the heating element when it is connected to a 230 V supply?

A circuit contains a 6 volt battery and a bulb with a resistance of 3 ohms. Calculate the current.

What is the voltage of a circuit with 15 amps of current and toaster with 8 ohms of resistance?

A circuit contains two 1.5 volt batteries and a bulb with a resistance of 3 ohms. Calculate the current.

You have a large flashlight that takes 6 D-cell batteries. If the current in the flashlight is 2 amps, what is the resistance of the light bulb? (Hint: A D-cell battery has 1.5 volts.)__________________

Circuits!

Electric Circuit: an electrical device connected so that it provides one or more complete paths for the movement of charges.

Series Circuit

Schematic Diagram: a graphic representation of an electric circuit or apparatus with standard symbols for the electrical devices.

Key Parts of a circuit: