P10: Need to know terms and formulae Flashcards
Nemonic for remembering electromagnetic spectrum
Rich Men Invent Very Unusual Xray Guns
In order of decreasing wavelength (i.e. largest to smallest wavelength)
- Radiowaves
- Microwaves
- Infrared waves
- Visible light
- ultraviolet waves
- Xrays
- Gamma Rays
Tool to remember circuit calculations
- Draw 5 triangles in the order shown in the diagram
- place one unit symbol at each vertex of each triangle and between the vertices of adjacent triangles starting from the left and in an up-down pattern.
- The symbols to be selected are taken from the nemonic:
Can Julie Visit W***_atson _***A***_nd _***C***_arry _***S***_ome _***Jellybeans With A***_ssorted _***Raisins?
Each triangle represents a triangle formula
What is a solar cell?
Electrical cell that produces a voltage when in sunlight.
What is specific heat capacity?
Energy needed by 1kg of the substance to raise its temperature by 1 Kelvin.
What is a solar heating panel?
Sealed panel designed to use sunlight to heat water running though it.
What is alpha radiation?
Alpha particles consisting of two protons and two neutrons emitted by unstable nuclei.
What is beta radiation?
Beta particles that are high-energy electrons created in and emitted from unstable nuclei.
What is gamma radiation?
Electromagnetic radiation emitted from unstable nuclei in radioactive substances.
What is the half-life of a radioactive isotope?
Average time taken for the number of nuclei of the isotope in a sample to halve.
What is nuclear fission?
The process in which certain nuclei spilt into two fragments, releasing energy and two or three neutrons as a result.
What is nuclear fusion?
The process in which small nuclei are forced together so they fuse with each other to form a larger nucleus.
What is activity?
The number of atoms of a radioactive substance that decay each second.
What is an atomic nucleus?
Tiny positively charged object composed of protons and neutrons at the centre of every atom.
What is a CT scanner?
A medical scanner that uses X-rays to produce a digital image of any cross section through the body or an organ.
What is an atomic number?
The number of protons in an atom.
What is ionisation?
Any process in which atoms become charged.
What is alternating current?
Electric current in a circuit that repeatedly reverses its direction.
What is a circuit breaker?
An electromagnetic switch that opens and cuts the current off if too much current passes through it.
What is a Coulomb?
-The unit of electrical charge. -Equal to the charge passing a point in a circuit in 1 second when the current is 1A.
What is direct current?
Electric current in a circuit that is in one direction only.
Define earthed.
Connected to the ground by means of a conducting lead or wire.
What is electric current?
-Flow of electric charge. -The size of an electric current is the rate of flow of charge.
What is electrical energy?
Energy transferred by the movement of electrical charge.
What is electromagnetic induction?
The process of inducing a potential difference in a wire by moving the wire so it cuts across the lines of force of a magnetic field.
What are electromagnetic waves?
-Electric and magnetic disturbances that transfer energy from one place to another. -The spectrum is ordered in increasing wavelengths.
What is frequency of an alternating current?
The number of complete cycles an alternating passes through each second.
What is a fuse?
A fuse contains a thin wire that melts and cuts the current off if too much current passes through it.
What is a kilowatt?
1000 Watts
What is a kilowatt-hour?
Electrical energy supplied to a 1kW electrical device in 1 hour.
What is a neutral wire?
The wire of a mains circuit that is earthed at the local sub-station so its potential is close to zero.
What is the North pole?
North-pointing end of a freely suspended bar magnet or of a magnetic compass.
What is Ohm’s Law?
The current through a resistor at constant temperature is directly proportional to the potential difference across the resistor.
What is an Ohmic conductor?
A conductor that has a constant resistance and therefore obeys Ohm’s law.
What is an oscilloscope?
A device used to display the shape of an electrical wave.
What is a parallel setup?
Components connected in a circuit so that the potential difference is the same across each one.
What is potential difference?
A measure of the work done or energy transferred to the lamp by each coulomb of charge that passes through it.
What is resistance?
-Resistance = pd / current -Opposition to the flow of an electric current.
What is a series setup?
Components connected in a circuit so that the same current passes through them.
What is the south pole?
South-pointing end of a freely suspended bar magnet or of a magnetic compass.
What is a split-ring commutator?
Metal contacts on the coil of a DC motor that connects the rotating coil continuously to its electrical power supply.
What is static electricity?
Charge “held” by an insulator or an insulated conductor.
What is a step-down transformer?
Electrical device used to step-down the size of an alternating voltage.
What is a step-up transformer?
Electrical device used to step-up the size of an alternating voltage.
What is a load?
-The weight of an object raised by a device used to lift the object. -The force applied by a device when it is used to shift an object.
What are magnetic poles?
Ends of a bar magnet or a magnetic compass.
What is the motor effect?
When a current is passed along a wire in a magnetic field and the wire is not parallel to the lines of the magnetic field, a force is exerted on the wire by the magnetic field.
What is amplitude?
-The height of a wave crest or a wave trough of a transverse wave from the rest position. -The maximum distance moved by an oscillating object from its equilibrium position.
What is an angle of incidence?
Angle between the incident ray and the normal?
What is the angle of reflection?
Angle between the reflected ray and normal.
What is a converging lens?
A lens that makes light rays parallel to the principal axis coverage to a point.
What is diffraction?
The spreading of waves when they pass through a gap or around the edges of an obstacle which has a similar size as the wavelength of the waves.
What is a diverging lens?
A lens that makes light rays parallel to the axis diverge as if from a single point.
What is the Doppler effect?
The change of wavelength of the waves from a moving source due to the motion of the source towards or away from the observer.
What is an echo?
Reflection of sound that can be heard.
What is a focal length?
The distance from the centre of a lens to the point where light rays parallel to the principal axis are focused.
What is frequency?
The number of wave crests passing a fixed point every second.
What is a longitudinal wave?
A wave in which the vibrations are parallel to the direction of energy transfer.
What is a transverse wave?
Wave in which the vibration is perpendicular to the direction of energy transfer.
What is magnification?
image height / object height
What is a magnifying glass?
A converging lens used to magnify a small object which must be placed between the lens and its focal point.
What is a mechanical wave?
Vibration that travels through a substance.
What is the normal?
Straight line through a surface or boundary perpendicular to the surface or boundary.
What is optical fibre?
Thin glass fibre used to send light signals along.
What is pitch?
The pitch of a sound increases if the frequency of the sound waves increases.
What is Snell’s Law?
-refractive index = sin i / sin r -i is the angle of incidence and r is the angle of refraction.
What is principal axis?
A straight line that passes along the normal at the centre of each lens surface.
What is the principal focus?
The point where light rays parallel to the principal axis of a lens are focused.
What is rarefaction?
Stretched apart.
What is a virtual image?
An image seen in a lens or mirror from which light rays appear to come after being refracted by the lens or reflected by the mirror.
What is a real image?
-An image formed where light rays meet. -An image formed by a lens that can be projected on a screen.
What is refraction?
The change of direction of a light ray when it passes across a boundary between two transparent substances.
What is a refractive index?
A measure of how much the substance can refract a light ray.
What is an ultrasonic wave?
Sound wave at frequency greater than 20,000Hz which is the upper frequency limit of the human ear.
What is wavelength?
The distance from one wave crest to the next.
What is white light?
Light that consists of all the colours of the visible spectrum.
What is amplitude?
-The height of a wave crest or a wave trough of a transverse wave from the rest position. -The maximum distance moved by an oscillating object from its equilibrium position.
What is gravitational field strength?
The force of gravity of an object of mass 1kg.
What is gravitational potential energy?
Energy of an object due to its position in a gravitational field.
What is Hooke’s Law?
The extension of a spring is directly proportional to the force applied provided its limit of proportionality is not exceeded.
What is hydraulic pressure?
The pressure in the liquid in a hydraulic arm.
What is the limit of proportionality?
The limit for Hooke’s Law applied to the extension of a stretched spring.
What is pressure?
Force per unit area for a force acting on a surface at right angles to the surface.
What is a Joule?
The unit of energy.
What is kinetic energy?
-Energy of a moving object due to its motion. -KE = mass x speed^2
What is mass?
-The quantity of matter in an object. -A measure of the difficulty of changing the motion of an object.
What is the centre of mass?
The point where an object’s mass may be thought to be concentrated.
What is a moment?
-The turning effect of a force defined by the equation. -moment of the force = force x perpendicular distance from the pivot to the line of action.
What is the principle of moments?
For an object in equilibrium, the sum of all of the clockwise moments about any point equals the sum of all of the clockwise moments about that point.
What is a pivot?
The point about which an object turns when acted on by a force that makes it turn.
What is momentum?
mass x velocity
What is a Newton?
The unit of force.
What is a Pascal?
The unit of pressure.
What is power?
The energy transformed or transferred per second.
What is useful energy?
Energy transferred to where it is wanted in the form it is wanted.
What is renewable energy?
Energy from sources that never run out.
What is acceleration?
Change of velocity per second.
What is resultant force?
The combined effect of the forces acting on an object.
What is a resultant moment?
The difference between the sum of the clockwise and the anticlockwise moments about the same point.
What is a simple pendulum?
A pendulum consisting of a small spherical bob suspended by a thin string from a fixed point.
What is speed?
distance moved / time taken
What is terminal velocity?
The velocity reached by an object when the drag force on it is equal and opposite to the force making it move.
What is velocity?
Speed in a given direction.
What is kinetic energy?
-Energy of a moving object due to its motion. -KE = mass x speed^2
What is wasted energy?
Energy that is not usefully transferred.
What is weight?
The force of gravity on an object.
What is geothermal energy?
Energy from hot underground rocks.
What is elastic potential energy?
Energy stored in an elastic object when work is done to change its shape.
What can a force do?
Change the motion of an object.
What is work?
Energy transferred by a force.
What is the centre of mass?
The point where an object’s mass may be thought to be concentrated.
What is centripetal acceleration?
-The acceleration of an object moving in a circle at constant speed. -Acts towards the centre of the circle.
What is conservation of energy?
The idea that energy cannot be created or destroyed.
What is conservation of momentum?
-In a closed system, the total momentum before an event is equal to the total momentum after the event. -Momentum is conserved in any collision or explosion provided no external forces act on the objects.
What is deceleration?
Change of velocity per second when an object slows down.
What is density?
Mass be unit volume of a substance.
What is drag force?
A force opposing the motion of an object due to fluid flowing past the object as it moves.
What is efficiency?
Useful energy transferred by a device divided by the total energy supplied to the device.
What is effort?
-The force applied to a device used to raise a weight or shift an object.
What is elastic?
A material is elastic if it is able to regain its shape after it has been squashed or stretched.
what is the solenoid rule?
The current induced in a solenoid always acts in such a direction as to oppose the change that causes it
