8j:Magnets and electromagnets

the poles of a magnet are called
1. north and south
2. plus and minus
3. east and west
4. positive and negative
2 north poles will
1. repel each other
2. attract each other
3. not affect each other
4. create a voltage between them
iron filings can show us the shape of the
1. lines of force
2. electric field
3. current flow
4. repulsion
in the Arctic, there is a
1. south magnetic pole
2. north magnetic pole
3. north and south magnetic pole
4. no magnetic pole
when a current flows in a conductor,
1. a magnetic field appears around the conductor
2. it will attract a nearby conductor
3. one end of the conductor acts as a north pole
4. the wire will not become warmer
which of these will make an electromagnet weaker?
1. replace the iron core with copper
2. increase the current
3. wind more "turns" on to the coil
4. give it an iron core
a relay is
1. a switch that is operated by an electromagnet
2. a coil
3. a type of fuse
4. part of a light bulb
an advantage of using a circuit breaker instead of a fuse is that
1. a circuit breaker is easier to reset
2. a fuse is cheaper
3. a circuit breaker can cope with higher currents
4. there is no advantage
a loudspeaker contains
1. an electromagnet, a permanent magnet, a paper cone
2. an electromagnet, a diaphragm, a paper cone
3. a permanent magnet, a relay, a battery
4. an electromagnet, a battery, a paper cone
in the Antarctic, there is
1. a north magnetic pole
2. a south magnetic pole
3. a north and south magnetic pole
4. no magnetic pole
a north and a south magnetic pole will
1. attract each other
2. repel each other
3. not affect each other
4. create a voltage between them
the magnetic field around an electromanget coil is
1. the same shape as the field around a bar magnet
2. circular
3. at right angles to the field around a bar magnet
4. opposite to the Earth's magnetic field
which of these will make an electromagnet stronger?
1. give it an iron core
2. decrease the current
3. give it an aluminium core
4. use thicker wire
Iron is "magnetically soft". This means that if you use it as the core of an electromagnet,
1. it does not stay magnetised when you switch off
2. it stays magnetised when you switch off
3. it does not make the field stronger
4. it obstructs the lines of force
we do not use steel for electromagnet cores, because
1. it would stay magnetised when you switch the electromagnet off
2. it would not stay magnetised when you switch the electromagnet off
3. it would not make the field stronger
4. it would require more current
relays are useful because
1. we can use delicate electronic devices to control high-current devices
2. they reduce the cost of building a circuit
3. they make a circuit more reliable
4. they can be used instead of fuses
a magnet can be ruined by
1. dropping it onto a hard floor, heating it
2. heating it, keeping it in a metal box
3. keeping it in a metal box, dropping it onto a hard floor
4. heating it, keeping it near a compass
which of these metals is affected by a magnet?
1. iron
2. copper
3. aluminium
4. gold
which of these metals are all affected by a magnet?
1. iron, cobalt, nickel
2. iron, aluminium, nickel
3. iron, copper, nickel
4. aluminium, cobalt, nickel
naturally-occurring magnets are called
1. lodestones
2. leadstones
3. north stones
4. compass stones
which of these is not needed to create an electromagnet?
1. bulb
2. battery
3. wire
4. iron core
the Earth's magnetic field is caused by
1. the movements of the earth's liquid interior
2. large amounts of iron at the north pole
3. large amounts of iron at the south pole
4. charged particles from the Sun striking our atmosphere
which way would your compass point if you were stood at the Earth's magnetic north pole?
1. downwards
2. towards the south pole
3. towards the equator
4. it would spin
the shape of the Earth's magnetic field is
1. as if there were a huge bar magnet inside the Earth
2. spherical
3. as if there were a huge horseshoe magnet inside the Earth
4. none of these
computer floppy disks are coated with
1. iron oxide
2. copper oxide
3. iron
4. steel
which of these are all places where electromagnets are used?
1. eye surgery, scrapards, loudspeakers
2. eye surgery, light bulbs, loudspeakers
3. scrapyards, loudspeakers, thermostats
4. thermostats, eye surgery, motors
which of these are all places where electromagnets are used?
1. motors, dynamic microphones, scrapyards
2. electric drills, scrapyards, electric ovens
3. dynamic microphones, electric drills, light bulbs
4. light bulbs, electric motors, loudspeakers
which of these are all places where electromagnets are not used?
1. light bulbs, electric ovens, switches
2. electric fridges, switches, light bulbs
3. loudspeakers, scrapyards, electric motors
4. televisions, light bulbs, switches
A compass needle will point to
1. a place in northern Canada
2. the earth's north pole
3. the equator
4. a place in Greenland
In a relay, the best material to make the armature (moving part) out of would be
1. iron
2. copper
3. aluminium
4. brass