Physics key terms Flashcards
What is an alternator?
An alternating current generator.
What is an angle of incidence?
The angle between the incidence (incoming) ray and the normal.
What is an angle of reflection?
The angle between the reflected (outgoing) ray and the normal.
What is a black dwarf?
A star that has faded out and gone cold.
What is Boyle’s law?
For a fixed mass of gas at a constant temperature, its pressure multiplied by its volume is constant.
What are carrier waves?
Waves used to carry any type of signal.
What is centripetal force?
The resultant force towards the centre of a circle, acting on an object moving in a circular path.
What is a ‘charge-coupled device’ (CCD)
An electrical device that creates an electronic signal from an optical image formed on the CCD’s array of pixels. E.g. in a digital camera.
What is a concave (Diverging) lens?
A lens that makes parallel rays diverge (spread out).
What is a contrast medium?
X-ray absorbing substances used to fill a body organ so the organ can be seen on a radiograph.
What is CMBR (Cosmic Microwave Background Radiation)?
Electromagnetic radiation that has been travelling through space ever since shortly after the Big Bang.
What is dark matter?
Matter in a galaxy that cannot be seen. Its presence is deduced because galaxies would spin much faster if their stars were only (visible) matter.
What is diffuse reflection?
When light rays are scattered in different directions.
What is driving force?
The force of a vehicle that makes it move AKA Thrust
What is a dynamo?
A direct current generator.
What is an electromagnet?
An insulated wire wrapped around an iron core that becomes magnetic when there is a current in the wire.
What is electromagnetic induction?
The process of inducing a potential difference in a wire by moving the wire so that it cuts across the lines of a magnetic field.
What is meant by focal length?
The distance from the centre of a lens to the point where light rays parallel to the principal axis are focussed (or in the case of a diverging lens, appear to diverge from).
What is frequency of oscillating motion?
The number of complete cycles of oscillations per second. Equal to 1 ÷ the time period.
What is the generator effect?
The production of a potential difference using a magnetic field.
What is Hooke’s law?
The extension of a spring is directly proportional to the force applied, as long as its limit of proportionality is not exceeded.
What is inertia?
The tendency of an object to stay at rest or to continue in a uniform motion.
What is the limit of proportionality?
The limit for Hooke’s law applied to the extension of a stretched spring.
What is a magnetic field line?
Line in a magnetic field along which a magnetic compass points – also called a line of force.
What is a magnifying glass?
- A converging lens
- Must be placed between the lens and its focal point.
What is a main sequence?
The main sequence is the life stage of a star during which it radiates energy because of fusion of hydrogen nuclei in its core. (The main bit)
What is a mechanical wave?
A vibration that travels through a substance.
Where are microwaves on the EM spectrum?
Between infra-red radiation and radio waves.
What is a moment?
The turning effect or force
Moment of a force (Nm) =
force (N) x perpendicular distance from the pivot (m).
What is the motor effect?
- When current is passed along a wire in a magnetic field
- The wire isn’t parallel to the lines of the magnetic field
- A force is exerted on the wire by the magnetic field.
What is a neutron star?
The highly compressed core of a massive star that remains after a supernova explosion.
What is Newtons first law of motion?
If the resultant force on an object is zero, the object stays at rest if it is stationary, or it keeps moving at a constant velocity (same speed and same direction).
What is Newtons seccond law of motion?
The acceleration of an object is proportional to the resultant force on the object, and inversely proportional to the mass of the object. F=ma
What is Newtons third law of motion?
When two objects interact with each other, they exert equal and opposite forces on each other.
What is an opaque object?
Light CANNOT pass through it.
What is a parallelogram of forms?
A geometrical method used to find the resultant of two forces that do not act along the same line.
What is a principle focus?
The point where light rays parallel to the principal axis of a lens are focussed (or, in the case of diverging lenses, appear to diverge from).
What is the principle of moments?
For an object in equilibrium, the sum of all the clockwise moments about any point = the sum of all the anti-clockwise moments about that same point.
What is a protostar?
The concentration of dust clouds and gas in space that forms a star. Think PROTOTYPE = PROTOSTAR
Where are radio waves on the EM spectrum?
At the longest wavelength (Left hand side)
1m-10^4 m
What is a red giant?
- A star that has expanded and cooled (fusing helium nuclei instead of hydrogen nuclei)
- Becomes red and much larger and cooler
What is a red supergiant?
A massive star that has expanded and cooled (fusing helium nuclei instead of hydrogen nuclei).
What is specific heat capacity?
The energy needed to raise the temperature of 1 kg of a substance by 1°C
What is specific latent heat of fusion?
The energy needed to melt 1 kg of a substance with no change of temperature.
What is specific latent heat of vaporisation?
The energy needed to boil away 1 kg of a substance with no change of the temperature.
What is specular reflection?
Reflection from a smooth surface. Each light ray is reflected in a single direction.
What is a split-ring communicator?
Metal contacts on the coil of a direct current motor that connects the rotating coil continuously to its electrical power supply.
What is a spring constant?
Force per unit extension of a spring.
What is a translucent object?
Light PASSES through but SCATTERED or REFRACTED
What are transverse waves?
A wave where the vibration is perpendicular to the direction of energy transfer. The wave direction is at 90° to the oscillations. (The wiggly one)
What are longitudinal waves?
Waves in which the vibrations are parallel to the direction of energy transfer. The wave direction is the same as the oscillations. eg |||| | | |||| | | |||| | | |||| | | |||| | | ||||
What is ultrasound?
- Sound waves with a frequency >20000hz.
- Above human hearing
Where is UV light on the EM spectrum?
Between visible light and X-rays. 10^ -8 m
What is a white dwarf?
A star that has collapsed from the red giant stage to become much smaller, hotter, and denser.
Where are X-rays on the EM spectrum?
Between UV and gamma rays 10^ -8 m
What EM waves are there?
Where on the EM spectrum do they appear?
EM waves (from longest to shortest wavelength)
- Radio 1 m - 10^4 m
- Micro 10^ -2 m
- Infra red 10^ -5 m
- Visible light 10^ -7 m
- UV 10^ -8 m \
- X-ray 10^ -10 m |> Ionising
- Gamma rays 10^ -15 m /
