Cells & Batteries

Cells & Batteries A cell a device that converts chemical energy into electrical energy. A battery is two or more electric cells, joined and used as a source of electric current.

Where does electricity come from? Generators are the most common source of electricity Hydroelectric generators Coal fired generators Oil fired generators

Hydroelectric generators

Voltage of Cells & Batteries A volt is the unit used to measure voltage The SI unit is V The more voltage a cell has, the more energy is supplied to the electrons that leave the cell to produce an electric current

Voltage of Cells & Batteries Voltage in the Battery = Sum of Voltage in the Cells in the Battery Example: A flashlight uses 2 D-size batteries with 1.5 V cells. Voltage in the flashlight battery = 1.5 V + 1.5 V = 3 V

Measuring Voltage A voltmeter is used to measure voltage It looks like a galvanometer, but measures voltage not current.

Measuring Voltage To connect a voltmeter to a cell, Connect the positive (+) to positive (+) and Connect the negative (-) to negative (-)

Types of Cells & Batteries All cells have two features in common: 1) Presence of two different metals in the cell The metals are called the electrodes 2) Separation of the metals by a solution The solution is called the electrolyte

Types of Cells & Batteries All batteries contain: Electrodes  the metals An Electrolyte  the solution

Diagram of Zinc-Carbon Cell

Resistance A resistor is a device made of material that offers resistance to the flow of charges

Resistance For a current to exist in a wire, the electrons must move past the atoms within the wire. The greater the resistance of a material, the greater the amount of energy the electrons give up as they pass through it.

Resistance