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 Circuit 1.Source: provides electrical energy to the rest of the circuit. Example: battery 2.Load: converts electrical energy into other forms of energy. Example: toaster 3.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 through A circuit is open when the switch is open

Movement of Electrons Electrons flow in one direction through the circuit Electric 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 10 18

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