wrong questions Flashcards
(45 cards)
what surface should you use to investigate diffuse reflection
an irregular reflecting surface
explain why the velocity of the satellite in circular orbit changes as it orbits the earth (3)
the force of gravity causes the satellite to accelerate towards the earth/the satellite is constantly accelerating
the acceleration causes a change in direction
velocity changes because direction changes
explain why refraction happens at the boundary between the deep water and shallower water
velocity/speed is slower in shallow water
so edge of wave front entering shallow water slows down
but the part of the wave front in deeper water continues at a higher speed
so one part of the wave front changes speed before other parts of the wave front
why does the coil in an electric motor rotate continuously when current flows through the coil
the current creates a magnetic field
the magnetic fields interact to create a pair of forces acting in opposite directions which causes the coil to rotate
every half revolution, the two halves of the commutator swap from one carbon brush to the other
the commutator reverses the current/keeps the forces in the same direction, so the coil rotates in the same direction
describe what will happen to the star the same size as the sun between the main sequence stage and the end of the star’s life cycle (3)
expand to become a red giant
collapse to become a white dwarf
cool to become a black dwarf
equilibrium in a star
grivitational force inwards are balanced/in equilibrium with the forces as a reslt of fusion reactions outwards
(radiation pressure is allowed)
what is the advantage of repeating measurements and calculating the mean
to reduce the effect of random errors
gives more accurate mean
how does a moving coil loudspeaker produce a sound wave
alternating current creates a magnetic field around the coil
which interacts with the permanent magnet’s magnetic field
producing a resultant force on the coil, causing the coil/cone to move
when the direction of the current reverses, the direction of the force reverses, producing a sound wave
explain how fleming’s left hand rule can be used to predict the direction in which the copper rod will move (5)
!hold thumb, first finger and second finger of the left hand at right angles to each other!
second finger represents….(current pointing out of the paper)
first finger represents the field (pointing downwards)
thumb points in the direction of the force (which is right)
therefore the rod moves….
explain why the temperature of the brakes increases as they are used
work is done due to friction
causing an increase in the internal./thermal energy of the brakes
explain the effect of earth’s gravitational force on the motion of a satellite
gravitational force cuases the satellite to accelerate twoards the earth
this changes the direction of motion, but not the speed
so it changes the velocity of the satellite
explain in terms of wave fronts, why refraction happens at the boundary between air and glass
different parts of the wavefront enter the glass at different times
the velocity/speed is less in glass
so one part of the wave fronts changes speed before other parts
why is a direct current induced in the coil of a dynamo
the coil rotates, so it cuts magnetic field lines
a potential difference is induced across the coil
there is a complete circuit, so a current is induced
becuase each half revolution, the commutator switch brushes/contacts
the direction of current/potential difference does not reverse every half rotation/ the direction of the current/pd is the same every half rotation
the car aerial is connected to an electricla circuit in the car describe what happens in the electrical circuit when the car aerial absorbs radio waves
induces alternating current in the electrical circuit
with the same frequency as the radio wave
why does the car have a maximum speed
there is a maximum forward force provided by the motor
as the speed of the car increases air resistance increases
until air resistance is equal in size to forwards force
so the car can no longer accelerate so the car travels at terminal velocity
why an alternating current is induced in the coil of an alternator
the coil cuts magnetic field lines
a pd is induced across the coil
there is a complete circuit so a current is induced
every half turn the pd reverses direction
so every half turn the current changes direction
why slip rings
provides a continuous connection between the coil and the brushes
or
stops the wires from twisting together
why does the handle of the alternator becomes easier to turn when the alternator is disconnected from the transformer and the lamp
there is no induced current after disconnection
so no magnetic field produced around the coil
to oppose the movement of the coil
explained braking distance increase
increase speed
the faster the vehicle the greater the distance in the driver’s reaction time
condition of tyres, condition of road surface, wet/icy
affect friction
condition of brakes
reduced friction if poor brakes
increase mass/weight of vehicle
increase kinetic energy
explain possible dangers caused by a vehicle having a large deceleration when it is braking
brakes overheating
causes loss of control of vehicle/causes skid
two iron rods inside solenoid. why do iron rods move apart when the switch of circuit is closed
rods become induced magnets
with the same polarity at each end
why is changing two independent variables at the same time not a valid method
not possible to know the effect of one variable or the other
how does the big bang theory describe the universe when it began
very hot and dense
evidence that the universe began from a very small region
the furthest galaxies are moving the fastest
which suggests that the universe is expanding
