Power Point Presentation On Science Form 3 Electricity.

Electricity

Electricity • Electrical energy produced when electric current flows. • A source of electrical energy is any device that produced electrical energy.

Sources of electrical energy • • • •

Chemical cell Biomass fuel Solar cell Geothermal energy • Hydroelectric power

• • • •

Wind energy Tidal energy Fossil fuel Nuclear energy

Electric current • 2 types of electricity : a) electrical charges (electrostatic) b) electrical current • Electric current is produced when there is a flow of negative charges

Electric current : from positive to negative Electron : from negative to positive

Electric Current • Rate of flow of negative charges in a circuit • Unit : ampere (A) • Measuring device : ammeter • To measure current, ammeter must be connected in series, in a circuit.

Voltage • The force that is needed to make charges flow from one point to another in a conductor • Unit : voltage (V) • Measuring device : voltmeter • To measure voltage, voltmeter must be connected in parallel, in a circuit.

Resistance • The property of a substances that opposes the flow of electric current • A substance with very high resistance only allows a small current to flow through it. • Unit : ohm (Ω)

Resistance • Depends on : a) diameter/ thickness of conductor Big , small b) length of conductor long , short c) type of conductor tungsten , copper

Symbols

Voltage, current and resistance in a series circuit • Total current I = I1 = I2 = I3 • Total voltage V = V1 + V2 + V3 • Total resistance

Series circuit

Series circuit

Series circuit

Voltage, current and resistance in a parallel circuit • Total current I = I1 + I2 + I3 • Total voltage V = V1 = V2 = V3 • Total resistance 1/R = 1/R + 1/R + 1/R

Parallel circuit

Parallel circuit

Parallel circuit

The differences