Electric Circuits

Voltaic Cells A source of energy that generates an

electric current by chemical reactions involving two different metals or metal compounds separated by a solution that is a conductor.

A battery is a connection of two or more cells

A voltaic cell has two metal terminals called electrodes that are made of different metals with different abilities to hold onto electrons.

Electrodes are in a conducting paste called electrolyte.

Types of cells…Primary Cell : cannot be recharged

Secondary Cell : rechargeable

e.g. car battery

e.g. Zn-C cell

Wet Cell: electrolyte is a solution.

e.g. car battery

Dry Cell: electrolyte is a moist paste.

e.g. Zn-C cell

DON’T throw me in the garbage . . . take me to the landfill instead!

Fuel Cell

A cell that generates electricity through the chemical reactions of fuel that is stored outside the cell.

Example: hydrogen fuel cell combines hydrogen that is stored in a tank with oxygen from the air. The only by-products are heat and water.

Solar Cells

A cell that converts sunlight into electrical energy.

Renewable energy

Current Electricity

Is made up of moving electrons flowing through a suitable conductor.

Parts of an Electric Circuit1. Source: provides electrical energy to the rest of the circuit. Example: battery2. Load: converts electrical energy into other forms of energy. Example: toaster3. Conductor: provides a pathway for electrons to flow.4. Control: controls the flow of electrons. Example: switch or fuse.

You Try It!!

P. 445 # 2-5, 8

Open Circuit

A circuit that has a gap or a break. Electrons do not flow throughA circuit is open when the switch is

open

Movement of ElectronsElectrons flow in one direction through

the circuitElectric Current: the rate of movement

of electric charge; the flow of electrons. Example: river current

The electric charge passing by a point in a circuit is measured in large numbers of electrons. The unit of electric charge is the coulomb.

1 coulomb = 6.25 X 1018

Amperes

Unit for electrical current is called the ampere (A)

1 A in a circuit means that 1 C (coulomb) passes a given point in a circuit every second.

Measured using an ammeter

Electrical Resistance

The property of a substance that slows electric current and converts electrical energy to other forms of energy.

In many circuits a resistor is used to decrease the electric current through a part of the circuit.

Loads

Resistors or any other device that transforms electrical energy into heat, motion, sound or light.

Example: lightbulb, fan, speakers.

Voltage Voltage is also known as potential

difference It is the value that relates to the amount of

work that is done on each coulomb. Measured in volts Volt = 1 joule (j) per coulomb (C) Potential difference is the difference

between the electric potential energy per unit of charge at two points in a circuit.

Measured with a voltmeter

You Try it!!!

P.454 # 1, 2, 4, 7