YR 9 Physics

(RESISTANCE AND OHMS LAW NOT DONE)

how is electricity is caused by charged particles

Movement of energy through charged particles, like electrons or ions, only charged particles can allow electricity to move through them, due to free flowing electrons, therefore causing electricity. Charged particles have a property called electric charge, which means they can attract or repel other charged particles. Electric charge comes in two types: positive and negative.

Describe electrostatic attraction and repulsion, and their connection to like and opposite charges

Electrostatic attraction is when particles of different charges are attracted to each other (opposite charge), while particles of the same (like) charge will repel each other. Charged particles have a property called electric charge, which means they can attract or repel other charged particles.

Which materials are electrical conductors and why.

Materials in which electrons are held on loosely in the valence shell and flow freely between atoms are called electrical conductors.

e.g. copper metal

Which materials are electrical insulators and why.

Some atoms hold onto their electrons tightly and electrons do not move through these materials very well.  These materials are called insulators.

e.g. cotton fabric

Explain the process of static electricity

When one material has more conductivity (e) than the other, they will rub against each other. Electrons will move from more more conductive to less conductive, allowing them to have charges. The one that gains now has a negative charge while the one that lost has a positive charge, they have a charge imbalance.

How does static electricity lead to sparks

As a negatively charged object collects more electrons, it’s negative charge increases. These electrons are also repelling each other, however, and more electrons in the same space means more repulsion. Eventually, this repulsive force is enough to push the electrons through the air to a nearby object, or often the ground, as they jump. This is observed as an electrical spark. This electrical discharge neutralises the negative charge on the object.

How does electrical charge imbalance apply

Electrical charge imbalance applies to the different conductivity of materials, the greater the difference in conductivity the greater the spark, however if there is no different there will be no spark.

How charged objects can induce a charge in other object

If a charged object comes close to neutral object, it can cause a charge to appear in that object. This is called charge induction. The charged object induces a charge in the neutral object. This involves the charged object either attracting or repelling electrons in the neutral object, so that they move towards one side.

What is static electricity

Static electricity happens when electrons build up in one place and don’t move. ("Static" means not moving.)

What is current electricity

Current electricity happens when electrons are able to move through a pathway. In some circuits, they move in one direction, and in others, they switch directions back and forth.

What is an electrical conductor

Electrical conductors — materials through which electricity flows easily

• usually metals due to the presence of free electrons allows for easy electron flow

• liquids with free moving ions can conduct electricity too.

What is an electrical insulator

Electrical insulators — materials which do not allow electricity to flow easily

• materials in which electrons and ions are “held tightly” to the atom (i.e. no free charged particles)

• liquids with no ions, like oil, won’t conduct

how different materials are able to conduct electricity based on their chemical structure.

Metals are good conductors of electricity due to the presence of free ‘delocalised’ electrons. Which are free flowing particles, which allows electrons to easily flow through it. Ionic bonds, which are dissolved and now have free flowing ions with a partial charge allowing them to conduct electricity.

What is an electric circuit

path that transmits electricity

What is a power supply

a power supply to provide the electrical energy

What is a load

a load (or loads) in which electrical energy is converted into other useful forms of energy (e.g. light, heat, sound)

What is a conducting path

a conducting path that allows electric charge to flow around the circuit.

What is current

The amount of electric charge flowing through a wire per second.

What is voltage

The electrical energy that pushes the electrons through a wire. Voltage is a measure of the energy that is pushing the electrons around a circuit. This energy is provided by the power supply (e.g. a battery or power pack).

What is current and voltage measured in

Current = Amps

Voltage = Volts

What is electric current

Electric current is the amount of electric charge flowing through a wire per second.

• Measured in amperes (A) (or Amps for short).

• The electric charge comes from the electrons.

How does current flow

Due to their negative charge, electrons in a powered circuit will flow from negative to positive. This is called electron flow (anode to cathode), however it is still common to to describe electric current as flowing from positive to negative, this is conventional current flow.

What is a series circuit

All the components of the circuit are connected one after the other to form a single loop. There is only one path for the current to flow.

What is a parallel circuit

Have a number of branching circuits, with each branch having its own components.

What are the characteristics of series circuit

The current (the amount of charge per second) is the same at each device. The voltage (the electrical energy pushing the electrons) is shared between the devices, depending on what each one needs, (voltage of loads)

What are the characteristics of parallel circuit

The current (the amount of charge per second) is split between the branches, depending on the components present in each branch. The voltage (the electrical energy pushing the electrons) will be the same through each branch. The battery must provide more current as you add more branches.

How is current measured

The size of the electric current in an electric circuit is measured by finding the amount of electric charge passing a particular point in an electric circuit every second. This is done using an ammeter.

How is voltage measured

Components such as light globes or speakers transform energy supplied into light, heat or sounds energy. The difference in energy the charges carry before the light globe or speaker is called the voltage drop. A voltmeter can measure the power supply or voltage drop across components of a circuit.

How is ammeter connected in a circuit

Red terminal (+) connected to (+) terminal of nearest cell.

Black terminal (-) connected to (-) terminal of nearest cell.

Always connected in SERIES 

1000 mA = 1 A

How is a voltmeter connected in a circuit

Red terminal (+) connected to (+) terminal of cell.
Black terminal (-) connected to (-) terminal of cell.
Old equipment had to be connected in PARALLEL to the device that you are looking at within the circuit

1000 mV = 1 V

how changes in current and voltage will affect a circuit

Increased voltage and current will lead to brighter and hotter light bulb filament. While increasing the voltage will also increase the current.

What is resistance

Resistance is a measure of how an object resists the flow of electrons

Resist the flow of electrons → controls the ease of the flow of current

Resistance is measured in ohms Ω

What is a resistor

Resistors do not allow current to flow through easily. Contain less loosely held electrons and more bonds between atoms which restrict pathways for electrons to flow

How do you draw a resistor

 Explain the impact of resistors/resistance on the load

The impact is that a larger resistor will decrease the current flow and increase the voltage (as you need to make it higher to push the current pass the resistor), in turn making the load dimmer or expend less energy since it doesn’t have it. But a smaller resistance will increase the current and decreases the amount of voltage needed making the light brighter.

Understand how current, voltage and resistance interact

Ohm's Law is a formula used to calculate the relationship between voltage, current and resistance in an electrical circuit.

What is the formula for Ohm’s law

Voltage = Resistance x Current

What is V, I and R defined as in ohm’s law

ΔV = the electric potential difference between two points on a circuit

I = the current between those two points

R = the total resistance of all electrical devices present between those two points