B6 - Brain and mind
Central nervous system (CNS) – Coordinates the body’s reaction.
Sensory neuron – carries electrical nerve impulse to the CNS.
Receptor – cells that detect the stimulus.
Stimulus – change in the environment.
Effector – Cells that carry out the response (muscular glands).
Response – how the body reacts to the stimulus.
Motor neuron – carries electrical nerve impulse from the CNS.
Neurons in your brain are connected together to form complicated pathways.
Ecstasy is the common name for the drug MDMA.
Ecstasy binds to the receptor where serotonin should bind.
The Central Nervous System (CNS) is the brain.
The gap in between a neuron is called a synapse.
P5 - Electric Curcuits
If you increase the voltage – then more current will flow…
… If you increase the resistance – then less current will flow.
Electric current is a flow of charge round a circuit. Its units are amperes, A.
In an electrical circuit the components and wires are full of charges that can move.
Current will only flow through a component it there’s a voltage across that component.
Voltage is the driving force that pushes the current round. Its units are Volts, V.
Resistance is anything in the circuit which slows the flow down. Its units are ohms, Ω.
A voltmeter measures potential difference between two points.
Units of charge are AMPS.
In an Insulator line plastic electrons fixed and charge cannot move around.
In a metal wire electrons are fixed to move and charge can flow.
Battery pushes charge around the wire (measures in volts).
Current depends on voltage and resistance.
One complete circuit is a series circuit.
Parallel circuits – V1=V2=V3, A=A1+A2, Total R<R, and Total R<R2
All components have electrical resistance.
Resistance decreases the current in the circuit, because it is stopping it.
A resistance is a component with a specific resistance.
If the current through a conductor is proportional to the voltage across it at constant temperature it is said to obey ohms law.
If a current/voltage graph is a straight line then the conductor obeys ohms law.
Resistance = Voltage/Current
Resistance x current = Voltage
Voltage/Resistance = Current
The resistance of a thermister decreases as temp increases.
It could be used to monitor the temp in a fridge and allow a circuit to turn the fridge on when the temp gets too low.
The resistance of a LDR decreases as light level increases…
…. It could be used as a sensor for a circuit that would turn on a street lamp at night.
Thermistor – resistance changes according to temperature.
LDR – resistance changes according to light.
Power (watts) = Current x Voltage
Word done (J) = Power x time (s)
Transformers change the voltage – but only AC voltages.
AC stands for alternating current – when the current is going up and down.
Transformers work by electromagnetic Induction.
Transformers use electromagnetic induction to ‘step up’ or ‘step down’ the voltage.
STEP – UP TRANSFORMERS step the voltage up. They have more turns on the secondary coil than the primary coil.
STEP – DOWN TRANSFORMERS step the voltage down. They have more turns on the primary coil than the secondary.
Potential difference (p.d.) the difference in potential energy (for each unit of charge flowing) between any two points in an electric circuit.
P6 - The wave model of radiation
A wave carries energy and information through the medium.
4 ways in which waves behave are: reflection, refraction, diffraction and inference.
A wave is a disturbance moving through a medium.
Parts of the medium move to and fro as the wave passes, but the medium does not move as a whole in the direction of the wave.
Wave speed = frequency x wavelength
In any given medium the wave speed is fixed. So the bigger the frequency, the smaller the wavelength.
Light behaves like a wave, showing diffraction and interference, if you look carefully.
The 3 highest – frequency types are ionizing: they cause chemical changes in materials that absorb them.
Electromagnetic waves can be used to carry information.
Medium means the material the wave is travelling through.