what type of magnet is a bar magnet an example of?
a permanent magnet
describe the relationship between distance and strength of a magnetic field
as distance increases, the strength of a magnetic field becomes weaker
explain how the electromagnet and conveyor belt are used to separate steel cans from the aluminium cans
- steel cans are attracted to the electromagnet and are transferred to the container
- aluminium cans are not attracted to the electromagnet and are left behind on the table
describe two ways to increase the strength of magnetic field at the top of the table
- raise the height of the table
- use a stronger electromagnet or use a larger current
why is the core made of iron?
iron is easily magnetised and demagnetised
why is steel, not iron, used to make permanent magnets?
magnetised steel does not lose its magnetism easily
describe how electromagnets are used in a scrapyard crane
- scrap vehicles are lifted in a scrap yard using powerful electromagnets attached to cranes
- the steel frame of a vehicle sticks to the electromagnet when current passes through the coil of the electromagnet
- when the current is switched off, the vehicle frame falls of the electromagnet
explain how an electromagnet is used in a circuit breaker
- a circuit breaker is a switch in series with an electromagnet
- the switch is held closed by a spring
- when the current is too large, the switch is pulled open by the electromagnet
- and it stays open until it is reset manually
suggest three changes that would decrease the force acting on the wire
- less current in the wire
- weaker field
- rotation of magnets so field is no longer perpendicular to the wire
what type of system uses a liquid to transmit a force?
hydraulic system
explain why a loudspeaker cone vibrates when an alternating current flows through the coil
- alternating current creates a magnetic field around the coil
- this magnetic field interacts with the permanent magnetic field
- this produces a resultant force and the coil moves
- when the direction of the current changes, the direction of the force changes to the opposite direction
explain how the ignition circuit works
- closing the ignition switch causes a current to pass through the electromagnet
- the iron core becomes magnetised
- the electromagnet attracts the iron arm
- the iron arm pushes the starter motor contacts together
- the starter motor circuit is complete
- a current flows through the starter motor which then turns
explain how a driver wearing a seat belt reduces the risk in the event of an accident
- seat belts are designed to stretch
- this increases the impact time
- so reduces the impact force
- seat belts spread the impact force across the chest
name two features in a car that reduces injury, other than seat belts
- crumple zones
- padded interior
- roll cage
- air bag
what is a force?
a push or pull acting on an object due to the interaction with another object
Describe the life cycle of stars much more massive than the Sun, including the formation of new elements.
- fusion processes in stars produce new elements
- cloud of gas and dust (nebula) pulled together by gravitational attraction
- causing increasing temperature to start the fusion process and become a protostar
- hydrogen nuclei fuse to form helium nuclei and the star becomes main sequence
- hydrogen begins to run out and helium nuclei fuse to make heavier elements up to iron
- the star expands to become a red super giant
- the star collapses rapidly and explodes called a supernova
- creating elements heavier than iron
- and distributing them throughout the universe
- leaving behind a neutron star or a black hole
which property of a star does the range of wavelengths depend on?
temperature
The alternator from the portable power supply is disconnected from the transformer and
lamp. Explain why the handle of the alternator becomes much easier to turn.
- there is no induced current
- so no magnetic field
- to oppose the movement of the coil
