Yr 10 Electricity- test note

Charge of an object is a result of electron transfer

  • Atoms are made of protons, neutrons, and electrons.

  • Protons don’t move, but electrons can move from one object to another.

    • Protons are inside the nucleus. Electrons are outside, so it can move.

  • When electrons are transferred, the object becomes charged.

    • Gain electrons → object becomes negatively charged

  • Lose electrons → objects become positively charged.

Examples:

  • Rubbing a balloon on your hair causes electrons to move from your hair to the ballon.

    • The balloon becomes negatively charged.

    • Your hair becomes positively charged.

Define current as a flow of charge

Notes:

  • Electric current is the flow of electric charge through a material (usually a wire)

    • Electrical current measures how many electrons are flowing in a circuit per second.

    • Measured using an instrument called Ammeter ( which is always placed in series with the circuit.

  • This charge is carried by electrons, which move through the circuit.

  • Current is the rate at which charge flows past a point in a circuit.

    • The unit for current is called an amperes.

Know that materials that do not allow charge to flow are called insulators

Notes:

  • Insulators are materials that do not allow electric charge to flow easily.

    • This is because their electrons are tightly bound and cannot move freely.

  • Insulators can stop us from getting electrocuted and are very often for this purpose (due to the water stored in the human body.)

Examples:

  • Electricians often use tools with plastic coated handles because plastic is a good insulator.

  • Plastic

  • Rubber

  • Glass

  • Wood

Know that materials that do not allow charge to flow are called conductors but that all conductors have resistance

Notes:

  • Conductors are materials that allow electric charge to flow easily because their electrons can move freely.

  • A flow of electrons in a conductor is called an electric current.

  • Even though conductors let charge flow, they still oppose the flow a little, this is called resistance.

    • This means it slightly slow down the flow of current and can produce heat.

Examples:

  • Copper

  • Aluminum

  • Silver

Know that the purpose of an electrical circuit is to charge electrical energy into useful energy such as heat, light, sound and movement

Notes:

  • An electrical circuit carries electrical energy from a power source to devices (components)

  • These devices convert electrical energy into other useful forms of energy.

Examples:

  • Light bulb: electrical energy → light and heat

  • Speaker: electrical energy → sound

  • Toaster: electrical energy → heat

Draw a circuit diagram from an actual circuit or a picture of a connected circuit using symbols

Notes:

  • Cells: supplies electrical energy. The larger terminal (on the left) is positive.

  • Battery: supplies electrical energy. ( supplies more than one cell)

  • Power pack: supplies electrical energy. (Voltage can be set to a desired value.

  • Wire: To pass current very easily from one part of a circuit to another.

  • Switch: An on-off switch allows current to flow only when it is in the closed (on) position.

  • Lamp: A lamp converts electrical energy to light.

  • Resistor: A resistor restricts the flow of current, and charges electrical energy to heat.

  • Variable resister (rheostat): A rheostat is usually used to connect the current in a circuit.

  • Fuse: A safety device which will blow if the current flowing through it exceeds a specified value.

  • Voltmeter: A voltmeter is used to measure voltage

  • Ammeter: An ammeter is used to measure current

  • Ohmmeter: An ohmmeter is used to measure resistance.

Know the difference between series and parallel circuit

Notes:

Series circuit>

  • Components are connected one after another in a single loop.

  • Same current flows through every component.

  • If one component (like a bulb) breaks, the whole circuit stops.

Examples:

  • Old Christmas lights

Parallel circuit>

  • Components are connected in separate branches

  • The current splits between the branches

  • If one component breaks, the other still work.

Examples:

  • Home wiring (each light or socket works independently)

Know that current is the rate of flow of charge in a circuit

Notes:

  • Current is the amount of electric charge that flows past a point in a circuit each second.

  • It tells you how fast the electrons are moving through the wire.

  • Measured in amperes (A) using an ammeter.

    • Higher current =more charge flowing every second.

Use an ammeter to measure the current in a circuit

Notes:

To use it as an ammeter>

  • It must be connected into the circuit in series

  • Choose the top and bottom terminals

  • Choose the scale setting 10A

To use it as a voltmeter>

  • It must be connected into the circuit in parallel

  • Choose the middle and bottom terminals

  • Choose the scale setting 20V

Describe how series and parallel circuits connections affect total resistance

Notes:

Series Circuit>

  • Total resistance increases as more resistors or components are added.

  • The current has only one path, so it had to go through every resistor

  • Total resistance is the sum of all resistors

Parallel circuit>

  • Total resistance decreases as more branches are added

  • The current has multiple paths, so it flows more easily.

  • The total resistance is less than the smallest resister in the circuit

    • More branches = more paths for current = lower resistance.

Describe how total resistance affects the current drawn from a battery

Notes:

  • Current (I) = Voltage (V) / Resistance (R)

  1. If total resistance increases

  • The current decreases (less current drawn from the battery)

  • The battery has a harder time pushing charge through

  1. If total resistance decreases

  • The current increases ( more current drawn from the battery)

  • It’s easier for charge to flow

Know where the energy comes from in an electrical circuit

Notes:

  • The energy in an circuit comes from the power source- usually a battery or power supply

  • The battery provides electrical energy by using stored chemical energy

  • This energy is transferred through the circuit to power components like bulbs, motors, or speakers

Know that it is resistance of a conductor which changes electrical energy into heat and light energy

Notes:

  • When electrical current flows through a conductor with resistance, some electrical energy is converted into heat and sometime light.

  • This is because resistance opposes the flow of electrons, causing them to collide and generate thermal energy (heat)

Examples:

  • A filament in a light bulb has high resistance, As current flows:

    • It heats up and glows → light energy

    • It also gives off heat

  • Toasters and electrical heaters work the same way - resistance wires converts electrical energy heat.

Know what voltage measures the energy carried by charge

Notes:

  • Voltage is a measure of the energy that each unit of charge carries in a circuit.

  • It tells us how much energy is being transferred to or from the components.

  • Measured in volts (V) using a voltmeter.

Example:

  • A 9V battery gives 9 joules of energy to every 1 coulomb of charge that flows.

Use a voltmeter to measure the energy change across components in circuits

Notes:

  • A voltmeter measures voltage, which tells us how much energy is gained or lost by the electric charge as it passes through a component.

  • The voltmeter is always connected in parallel with the component you’re measuring (like a bulb or resistor)

Know how the current and voltage affect the brightness of a lamp

Notes:

  • A higher voltage gives more energy to the charges, so the lamp shines brighter.

  • A higher current means more charge is flowing, delivering more energy per second - also making the lamp brighter.

State the purpose of a fuse in a circuit

Notes:

  • A fuse is a safety device in a circuit

  • It is designed to protect the circuit by breaking (melting) if the current gets too high.

  • This stops the flow of electricity and helps prevents fires or damage to components.

  • Too much current flows where there is an electric fault which causes a short circuit

    • Short circuits are caused by broken plugs, broken electrical wires and etc

Know the safety features of a three pin plug

Notes:

  1. Earth Pin (longest pin)

  • Connects to the earth wire for safety.

  • Directs excess current safely into the ground prevent electric shock.

  1. Fuse:

  • Inside the plug

  • Melts if too much current flows breaking the circuit and protecting appliances

  1. Plastic casing:

  • The plug is made of insulating plastic to prevent electric shock

  1. Cable grip:

  • Holds the wires firmly in place so they don’t loosen or touch each other

  1. Three wires:

  • Live wire ( brown): carries current to the appliance.

  • Neutral wire (blue): Returns current to the power source

  • Earth wire (green/yellow): safety wire to prevent shocks