physics Flashcards
how to calculate total resistance in a parallel circuit
(R1 x R2) / (R1 + R2)
how is distribution of current different in series and parallel circuits
in a series it’s the same everywhere and in a parallel it splits
how is voltage distributed in a series and parallel circuit
series: divided
parallel: same
how is resistance calculated in series and parallel circuits
series: add them all
parallel: R1 x R2 / R1 + R2
what is alpha radiation
2 neutrons and 2 protons
+2 charge and very ionising
low penetrating ability- stopped by paper
short distance travelled before stopped by air
what is beta radiation
an electron
-1 charge (moderately ionising)
medium penetrating ability- stopped by Al foil
medium distance travelled before stopped by air
what is gamma radiation
EM radiation
0 charge - not ionising
high penetrating ability - stopped by lead/concrete
long distance travelled before stopped by air
how can you show something is a permanent magnet
demonstrate that it can repel another permanent magnet
4 rules for magnetic field lines
start on north poles, end on south and form closed loops
can’t start or end in space
can’t cross one another
closer together when field is stronger
what is a soft magnetic material
easy to magnetise but also lose their magnetism easily eg iron
what is a hard magnetic material
difficult to magnetise but once they are magnetised they are difficult to demagnetise eg steel
why do electromagnets use soft magnets
they easily lose and gain magnetism
what things can cause a hard magnet to become demagnetised
hitting it or heating it
what kind of waves are sound waves
longitudinal
what are longitudinal waves
the medium moves parallel to the propagation of the wave
what are transverse waves
medium moves perpendicular to the propagation of the wave
which characteristics of a wave change when it enters water after travelling through air
speed and wavelength
what is current
rate of flow of charge
what happens to the electrical power as the electric potetial difference decreases
electrical power decreases because:
power = current x potential difference
what is sparking
when the air between 2 objects becomes ionised by a large voltage and therefore starts conducting
how can insulators become electrically charged by friction
when 2 insulators move relative to each other, friction between the 2 results in them becoming electrically charged (one positive and one negative)
what is a scalar quantity
one that has magnitude (size) but not direction
what is a vector quantity
one that has both magnitude and direction
how to calculate acceleration
change in velocity / time
what is the area under a speed time graph
distance
what is the area under a velocity time graph
change in displacement
what is hookes law
force = spring constant x extension
what is newtons first law
a body will remain at rest or in a state of uniform motion in a straight line unless acted on by an external resultant force
what is inertia
the resistance of any physical object to any change in its velocity
what is newtons second law
force = mass x acceleration
what is newtons third law
if body A exerts a force on body B then body B exerts an equal and opposite force of the same type on body A
how to calculate momentum
mass x velocity
what is thermal energy
the energy a substance has because of the motions of its microscopic particles
what is the difference between conduction and convection
in conduction heat is transferred by microscopic motions of individual particles. kinetic energy is passed from one particle to the next. but in convection heat is transferred by macroscopic motion of large numbers of particles- the particles themselves move around and take their kinetic energy with them
how to calculate latent heat
energy / mass
how to calculate frequency
1/ period or 1/T
how to calculate wave speed
distance/time or freq x wavelength
examples of transverse waves
all electromagnetic waves, waves on a string, seismic s waves
examples of longitudinal waves
sound, ultrasound, compression waves on a spring, seismic p waves
what is the law of reflection
incident angle = reflected angle
