Year 9 Science Exam Revision

What is the difference between conventional current and the flow of electrons?

Conventional current flows from positive to negative to positive to negative and the flow of electrons is negative to positive in a circuit.

Define Voltage

Voltage is the pressure from an electrical circuit's power source that pushes charged electrons around a circuit. The unit of voltage is the volts (V)

Define Current

Electric current is the flow of electric charge. A measure of the amount of electric charge passing through a particular point in an electric circuit every second. The unit of current is the ampere/amps (A) or sometimes milliamps (mA)

What is a circuit?

The pathway in which electrical energy flows. In which electical energy is transformed and used for lighting, heating, cooling and much more.

What are the three essential components of a circuit?

-Power Supply: provides the electrical energy e.g a battery

-Conducting Path: the path that allows electric charge to flow around the circuit eg. the wires

-Load or Loads: where electical energy is converted into other useful forms of energy

What is the symbol for a voltmeter?

What is the symbol for an ammeter?

What is the symbol for a light globe?

What is the symbol for a LED?

What is the symbol for a resistor?

What is the symbol for a variable resistor?

What is the symbol for a fuse?

What is the symbol for an open switch?

What is the symbol for a closed switch?

What is the symbol for a single celled battery?

What is the symbol for a double cell battery?

What is the symbol for wires?

Lines that must be ruled

How do you properly set up a LED?

The Anode which is the longer end in a small LED must face the positive terminal of the power source and the cathode which is the smaller end must face the negative terminal of the power source.

What is the difference between forwards and backwards bias?

Forward bias is when the LED is on and lighting up because it is connected properly and the anode is connected to positive. Backwards bias is the opposite and when the cathode is connected to positive and electricity will not flow through the LED.

What is a series circuit?

Is a closed circuit with the components joined one after the other in a single continous loop. An electron will pass through every part of the circuit.

What is a parrallel circuit?

Is a closed circuit where each component is connected in a seperate conducting path. Current divides in two or more paths before recombining and as such, electrons do not pass through every component around the circuit.

What is the difference between series and parrallel circuits?

A series circuit is one continous loop whilst parrallel circuits have components connected in seperate conducting paths. Electrons flow through every part of series circuit whilst they do not in a parrallel circuit.

What are some examples of series circuits in everyday life?

Christmas lights, Flashlights and Lamps

What are some examples of parrallel circuits in everyday life?

Traffic lights, Household wiring and Computer parts

How does current flow through a series circuit?

The amps are the same throughout the circuit and if more loads are added it stays the same but amount decreases.

How does current flow through a parallel circuit?

The total amount of amps is added up from the individual branches. Eg: if there is a parallel circuit with 2 branches and the total amps is 0.6A then each branch would measure 0.3A. If you add another branch then the total amps goes up but if you add another load to an existing branch then it stays the same if the resistance is the same.

How does voltage flow through a series circuit?

The total voltage is divided by each load. If another load is added then redivide it. Eg: If there were 9V with 2 loads and you added a third the voltage across the loads would be 3V.

How does voltage flow through a parrallel circuit?

The voltage is the same across a parrallel circuit. It only divides if there are multiple loads on the same branch.

How does brightness work in a series circuit?

Since brightness is dependent on both the current and voltage then all globes in the series circuit have the same voltage and current and so have the same brightness. Their brightness decreases with every globe added.

How does brightness work in a parrallel circuit?

Since brightness is dependent on both the current and voltage, all globes have the same voltage across them and share the electric current they have the same brightness. Except when there is multiple globes on the same branch and in that instance those two globes have the same brightness but are dimmer than a branch with only one globe on it.

Define resistance.

Electrical resistance is a measure of how difficult it is for electrons to flow through a part of a circuit.

What are some factors that influence the resistance of a wire?

If there are resistors on the circuit which cause a decrease in the amount of current flowing through the circuit. Additionally loads carry resistance which also is a factor.

What are some common examples of insulators?

Insulators are materials that slow and prevent the free flow of electons (they don't allow electricity the flow through or on them).

Rubber, plastic, glass, dry wood and oil.

What are some common examples of conductors?

Conductors are materials that permit electrons to flow freely and quickly through the substance.

Silver, gold, copper, steel and water.

How do you calciulate resistance using Ohm's law?

R= V/I (Voltage divided by current)

V= Voltage

I= Current

How do you calculate current using Ohm's law?

I= V/R (Voltage divided by resistance)

R= Resistance

V=Voltage

How do you calculate voltage using Ohm's law?

V= IxR

R= Resistance

I= Current

Homeostasis

Is the maintenance of the body's stable internal environment despite significant changes internally or externally.

What are the 5 parts of the stimulus response model?

Stimulus, Receptors, Command Centre, Effectors and Response

Stimulus

A change in internal or external environment

Receptor

The part of the body that detects the stimulus

Command Centre

The processing centre that decides if action needs to be taken

Effector

A cell, tissue or organ that responds and creates the control centre's signal

Response

A desired change in the function of the target cell, tissue or organ

The Nervous System

Is a communication network that controls all the other systems in your body

Central Nervous System

Consists of brain and spinal cord

Peripheral Nervous System

Consists of the nerves that branch out from the brain and spinal cord

Somatic Nervous System

Controls actions that we do by choice ex. walking and moving arms. Part of PNS

Autonomic Nervous System

Controls involuntary bodily functions. ex. breathing and heart rate. Part of PNS

Sympathetic Nervous System

Is a part of the autonomic nervous system that arouses body to expend more energy

Parasympathetic Nervous System

Is a part of the autonomic nervous system that relaxes the body to conserve and maintain energy

Signaling Molecule

Molecules that transmit information between cells, enabling communication and coordination in multicellular organisms

Neurons

They are specialised nerve cells that allow electrical messages to pass through them.

What are the parts of the Neuron?

Dendrites, Cell Body, Nucleus, Axon, Myelin Sheath, Axon Terminals

Nerves

Is a bundle of fibers that recieves and sends messages between the body and brain.

Dendrites

Are branching extensions of the cell body to receive neurotransmitters from the axon terminals of the neuron before it.

Axon

Is a long structure that carries the electrical message from the dendrites and cell body to the axon terminals.

Cell Body

Contains the nucleus of the neuron.

Axon Terminals

Receives the electrical message from the axon and transports it across the synapse to the next part of the body. (Can be a neuron or other type of tissue/cell)

Myelin Sheath

Is an insulating substance that covers the axon speeding up the messages that travel through it.

Action Potential

is a rapid temporary chage in electrical charge along a neuron from the dendrites, along the axon and to the axon terminals.

Synapse

is the gap between neurons.

Neurotransmitter

Are chemical messengers which are released from one neuron and cross the synapse to cause an action potential in the next neuron.

Conscious Response

Are messages passed from sensory neurons through the spinal cord up to the brain where it makes a decsion which travels back down the spinal cord and moves along the motor neurons to the effector. KEY PART IS GOES ALL THE WAY TO BRAIN.

Unconscious Response

Is an automatic response to a stimulus that does not travel all the way to the brain but instead just the spinal cord and requires no conscious thought. KEY IS THAT IT DOES NOT TRAVEL TO THE BRAIN INTIALLY.

Reflex Action

A reflex action is an involutary action of the body. ex. knee jerk or movement of your hand away from a hot flame.

Reflex Arc

Is a neural pathway that controls an action reflex.

Hormones

Are signaling molecules that carry messages to specific target cells or organs through the circulatory system.

Glands

Are organs that produce hormones which are released into the bloodstream.

Feedback Loop

Is a continuous cycle of monitering conditions and detecting and responding to changes.

Negative Feedback Loop

Occurs when the response to a stimulus reverses or is opposite to the stimulus, returning the body to how it was before the stimulus. ex. blood glucose levels, temperature

Insulin

Is a hormone released by the pancreas when blood glucose levels are too high to tell cells to intake glucose whilst also tell the liver to store excess glucose as glycogen.

Glucagon

Is a hormone released by the pancreas when your blood glucose levels are too low, telling your liver to release stored glucose into the bloodstream.

Glycogen

Is a stored form of glucose found mostly in the liver and muscle cells.

Positive Feedback Loop

Is a feedback loop that increases the stimulus or goes in the same direction as it. ex. childbirth where hormones are released causing contractions this causes more hormone release which creates more hormone etc

What is the difference between a Positive and Negative feedback loop?

The difference between a positive and negative feedback loop is that whilst a negative feedback loop reverses the stimulus, a positive feedback loop increases the stimulus and goes in the same direction.

Atom

The basic building block of life made up of 3 different subatomic particles; protons, neutrons, and electrons and is the smallest possible unit of matter.

Proton

A positively charged sub-atomic particle found in the nucleas of an atom with a relative mass of 1. (Number of protons unique to every element.)

Neutron

A neutrally charged sub-atomic particle found in the nucleas of an atom with a relative mass of 1.

Electron

A negatively charged sub-atomic particle found orbiting the nucleas of an atom in electron shells with a relative mass of 1/1000.

Atomic mass number (A)

The total number of protons and neutrons in an atom.

Atomic Number (Z)

Atomic number is equal to the amount of protons in an atom. (Unique to every element)

Ion

An ion is an element that is not netrally charged and therefore has an overall postive or negative charge from an increased or decreased amount of electrons not equally the number of protons.

Cation

A cation is a positively charged ion because it has more protons than electrons. Has lost electrons to have a full valence shell.

Anion

An anion is a negatively charged ion that has gained electrons from another to fill its valence shell giving it more electrons than protons.

Ionic Compound

An ionic compound is when an anion and cation come together to form a compound. Cation loses electrons which the anion gains.

Valence Shell

The outermost electron shell in an atom that is involved in chemical bonding.

Valence Electron(s)

Electrons found in the valence shell.

Octet Rule

Is the tendency for atoms to prefer to have full valence shells by losing or gaining electrons.

Electrostatic attraction

Is the force that pulls oppositely charged particles toward each other. Cations and anions have this attraction and come together forming an ionic bond.