feb mocks Flashcards
what are the two equations for acceleration?
a = (v-u)/t
v squared = u squared x 2as
what is friction?
a force that opposes motion
what is the relationship between force, mass, and acceleration?
F=ma
what is the relation ship between weight, mass, and gravitational field strength?
w=mg
what are the factors affecting stopping time?
speed, mass, road condition, tyre condition, and reaction time
what is elastic behaviour?
the ability of a material to recover its original shape after the forces causing deformation have been removed
how does insulation protect the device/user?
the copper wires are wrapped in an insulating material so it doesn’t come into contact with the user
how does double insulation protect the user and device?
- only for metal cases
- a layer of insulation is put around the case to prevent the person being electrocuted
how does earthing protect the user and device?
- if the live wire touches the metal casing it can become electrified and could electrocute the user
- the earth wire provides a low resistance path to the earth
- there is a surge in current in the earth wire and so also in the live wire
- so the fuse melts and breaks the circuit
how do fuses protect the user and device?
melts if the current is too high, has to be replaced
how do circuit breakers protect the user and device?
- automatic electromagnets
- same job as fuse but can be reset and reused
- works faster than fuses
what is the relationship between power current and voltage?
P=IV
what is the relationship between energy transferred, current, voltage and time?
E=IVt
what is ac?
current constantly changes direction, supplied by mains electricity
what is dc?
current always flows in the same direction, supplied by cells or batteries
what are the advantages of a parallel circuit?
- components can be switched on/off independently
- circuit still works if one breaks
- bulbs have similar brightness
what are the advantages of a series circuit?
- less wires
- less power
- cheaper
- easier to assemble
how is the current in a series circuit affected by the number of components?
more things in circuit = less current overall
how does resistance in a LDR vary with illumination?
more illumination = less resistance
how does a thermistor vary with temperature?
temp increases = resistance decreases
what is current?
the rate of flow of charge
what is electric current in solid metallic conductors?
negatively charged electrons
what is voltage?
energy transferred per unit time
what is a volt?
joule per coulomb
can all waves be reflected and refracted?
yes
what are the uses of radiowaves?
broadcasting and communications
what are the uses of microwaves?
cooking and satellite transmissions
what are the uses of infrared?
heaters and night vision
what are the uses of visible light?
optical fibres and photography
what is the use for ultraviolet?
fluorescent lamps
what are the uses of xrays?
observing internal structure of objects
what are the uses of gamma rays?
sterilising foods and medical equipment
what are the dangers of microwaves?
internal heating of body tissue
what are the dangers of infrared?
skin burns
what are the dangers of ultraviolet?
damage to surface cells and blindness
what are the dangers of gamma rays?
cancer, mutations of cells
what kind of waves are light waves?
transverse
what kind of waves are sound waves?
longitudinal
what is specific heat capacity?
the energy required to change the temperature of an object by one degrees celcius per kg of mass
what is the thumb in flhr?
force
what is the index finger in flhr?
magnetic field
what is the middle finger in flhr?
current
what is the nature of alpha?
2 neutrons, 2 protons
what is the nature of beta?
one electron
what is the nature of gamma?
em wave
what is irradiation?
when an object is exposed to radiation
what is the role of control rods?
absorb neutrons and completely remove them from the fission process, helps adjust rate of nuclear fission in reactor
what are control rods made of?
boron or cadmium
what is the role of moderators?
slow down/absorb the KE of neutrons
what are moderators made of?
graphite
what is the shielding of a nuclear reactor made of?
the vessel is made of steel then surrounded by a thick layer of concrete
