Electricity and magnetism

• Energy is the ability to do work and is measured in joules (J).
• People use energy to run, plants need energy from the sun to continue living, cars need energy from fuel to move, and light from a bulb is produced by energy.
• Energy cannot be created nor destroyed and can exist in various forms such as:

  • sound energy
  • kinetic energy
  • electrical energy
  • gravitational potential energy
  • elastic potential energy
  • nuclear energy
  • light energy
  • heat energy
  • chemical energy.
• Electric shock when touching a grocery trolley is due to the transfer of electrostatic charges between our body and the trolley.
• Electric charges consist of positive charges (protons) and negative charges (electrons), and attraction and repulsion between them are known as electrostatic forces.
• When two different objects are rubbed together, only electrons are transferred, resulting in one object becoming negatively charged and the other positively charged.
• A comb rubbed with a woollen cloth gains electrons and becomes negatively charged, attracting pieces of neutral shredded paper.
• An electroscope is a device used to detect the existence of electric charges on an object, with the gold leaf diverging due to the repulsion between like charges.
• Examples of electrostatic in daily life include the charging of clouds through friction with air, resulting in lightning, and the use of lightning conductors to provide a path for electric charges to flow into the ground.
• Electric current is the rate of flow of electric charges through a conductor, measured in amperes (A).
• Voltage is the potential difference between two points, measured in volts (V).
• Resistance is the ability of a conductor to limit or resist the flow of electric current, measured in ohms (Ω).
• Ohm's Law states that the electric current (I) is directly proportional to the voltage (V) across a conductor, provided the temperature and other physical situations remain unchanged.
• Ohm's Law equation: V = IR, where V is voltage, I is current, and R is resistance.
• A series circuit is made up of electrical components that are connected one after another where the current flows through in a single path.
• In a series circuit, the current is the same through all components, the voltage is the sum of the individual voltages, and the resistance is the sum of the individual resistances.
• In a series circuit, the effective resistance is the sum of the individual resistances.
• In a series circuit, the current can be calculated using Ohm's Law (I = V/R).
• In a series circuit, the voltage across each component can be calculated by multiplying the current by the resistance of the component.
• Advantages of a series circuit include every component receiving the same amount of current and an increase in voltage supplying more electric current.
• In a series circuit, I = I1= I2=...
• In a series circuit, V = V1 + V2 + ...
• In a series circuit, R = R1 + R2 + R3 + R4
• The total resistance of a series circuit is equal to the sum of all resistances.
• A parallel circuit has multiple paths for electricity to flow through.
• In a parallel circuit, I = I1+I2+... (total current)
• In a parallel circuit, V = V1=V2=... (voltage across components)
• In a parallel circuit, 1/Rt = 1/R1 + 1/R2 + 1/R3 + 1/R4
• In a parallel circuit, the voltage remains constant throughout the circuit.
• In a parallel circuit, if one branch breaks or opens, it does not affect other branches.
• A parallel circuit is separated into several different paths of electrical circuit and each parallel path has electrical components.
• The voltage in a parallel circuit is the same across each component.
• Advantages of a parallel circuit include the ability to switch on or off each electrical appliance separately and the function of other appliances not being affected by the addition of more appliances.
• The current in a parallel circuit can be calculated by dividing the voltage by the resistance.
• Van de Graff generator: A device that produces a constant voltage by applying a constant current to a wire that is suspended in a container of air.
• Conductor: An object through which electricity flows easily.
• Insulator: An object that resists the flow of electricity.
• Resistance: The measure of how difficult it is for an electric charge to move through a material.
• Electroscope: used to detect electrical charges
• Voltmeter: used to measure voltage