All weeks

• Sound waves are produced by vibrating or oscillating objects and are transmitted faster in solids than liquids and gases because solid particles are very close to one another.
• the speed of sound in gases is affected by temperature. As the temperature increases, the speed of molecules also increases. As a result, molecules collide more frequently, thereby transmitting the disturbance more quickly.
• The visible spectrum is the portion of the electromagnetic spectrum that is visible to the human eye.
• the wavelength and frequency of light are inversely proportional
• The separation of visible light into its constituent colours is called dispersion.
• Refraction of light is the bending of light as it passes from one medium to another.
• Heat transfers from a higher temperature to a lower temperature.
• the absorbed light is emitted or released in different directions - Scattering of light
• Convection

  refers to the transfer of thermal energy by the movement of fluids.
• The transmission of thermal energy by conduction which

  occurs in solids and fluids (gases and liquids), but the effect is more evident in solids. 
• Radiation

  is the transfer of thermal energy by electromagnetic waves. 
• Electricity is the movement of electrons.
• Current - is a flow of electric charge in a circuit.
• Materials  that allow current to flow easily are called conductors
• those that do not allow current to flow are called insulators
• Electric current is represented by the symbol I.
• The unit used to express current is ampere (A).
• A device called ammeter is used to measure current.
• Just like any object, a charge is put into motion by an unbalanced force.  This unbalanced force is greater by voltage or potential difference.
• The charge flows when there is a difference in electrical potential between two points in a circuit. The direction of flow is from a place of higher potential to a place of lower potential.
• The voltage created by an electrical source is called electromotive force (EMF).
•  Voltage or potential difference is measured using a device called voltmeter. Voltage is expressed in volts (V).
• The opposition to the flow of electric charge is called resistance (R).
• Resistance is expressed in ohms whose symbol is Ω, the Greek capital letter omega.
• An ohmmeter is an electrical instrument that measures electrical resistance.
• Current - The rate at which charge is flowing.
• Voltage - The pressure from an electrical circuit’s power source that pushes charged electrons through a conducting loop. Difference of charges between two points.
• Resistance - A material’s tendency to resist the flow of charge.
• Current - I - A

  Voltage - V

  Resistance - R - Ω
• Ohm’s law states that the flowing current in a circuit is directly proportional to the voltage and inversely proportional to the resistance.
• I=V/R = I=V/R = V/R
• charge is represented by the amount of water
• voltage is represented by the water pressure
• current is represented by the water flow
• resistance is represented by the pipes
• The path in which the electrons flow is cut when the switch is turned off, the path is open (open circuit). 
• the switch is turned on, therefore, the path is closed (closed circuit).
• An electric circuit is consists of the following:

  • a source of electrical power (dry cell, battery,  household wall outlets, electric generator from power plants);
  • a load that needs electrical power to operate or resistance (electric bulb, any device or appliance), and;
  • a conductive path (wires or printed etches on a circuit board).
• The diagram that describes a circuit is called a schematic diagram.
• Schematic diagram

  A) single dry cell

  B) connecting wire

  C) open switch

  D) battery

  E) resistor

  F) closed switch