Magnetic Effects of Current HOTS 2 Flashcards
what is the si unit of mag field strength
it is a vector quantity
si unit: tesla
1 tesla=1N/amp.metere
cGS: Gauss
I tesla= 10⁴ gauss
what happens when a magnet is cut in half into in transverse/along length
bothcases new magnets produced
i)transverse
pole strrength same, mag moment changes
ii)length
pole strength and mag moment changes
mag moment refers to the force experienced by a magnet in an external magnetic field
a freely suspended magnet always aligns in the north south direction
earth is a huge magnet with its south pole lying somewhere near the geographical north and north pole lying somewhere near the geogpahical south
why are magnetic field lines closed continuous curves?
mag poles always exist in pairs. Ourside the magnet the directionof fied is from north->south. Inside it its from south->north, forming endless closed loops
give the uses of compassneedle
-plot the magnetic field around a bar magnet
-navigation of ships
-finding the posn of electrical wires in the walls whic are closed
define magnet? what are natural artificial magnet
magnets are subtances that have the property to attract fe,ni,co.
natural magnets are made of lodestone(fe3o4).
Since they have an irregular chape, pieces of iron and other magnetic materals are made to acquire natural magnetic properties and can be made to take a diff shape.
shapes: bar magnet/horshoe/circular/needke
name and explain the components of domestic electric circuit
i)Live wire and neutral wire: maintain p.d because live wire carry 220v of current and neutral wire 0V
ii)earth wire: safety measure protects us from severe chosk from casing of appliances
iii)Fuse:safety measure whenever current exceeds permissible limit, the fse melt and break the circuit
iv)electric meter records amount ofellectrical energy used
v)distrubution box several independent distrubution circuits are drwn to different parts of the house
vi)two seperate circuits- one is 5A circuit for lighter applieances lieke tubelight
-one is 15a circuit for heavy applieances with high power rating
what is snow rule and snbe rule?
SNOW
if current is from s-north and the wire is over compass needle, the head of needle deflects towards the west
SNBE
if current is from n->s ad the wire isbelow the compass needle, the head of needle deflects east
A current through a horizontal power line flows in east to west
direction. What is the direction of magnetic field at a point directly
below it and at a point directly above it?
The current is in the east-west direction. Applying the right-hand
thumb rule, we get that the magnetic field (at any point below or
above the wire) turns clockwise in a plane perpendicular to the wire,
when viewed from the east end, and anti-clockwise, when viewed
from the west end.
give reason: why a coil of a smaller radii has a greater magnetic field
snaller radii will be more field fo the same magnitude of current because b inversely proportional r(radius)
justify that B=n x b
Since the same current flows in the same direction produces the same magnetic field, the mag field produced due to each turn becomes additive
justify the mag field produced at centre of a coil of n turns is as large as produced by a single turn
i) the mag field lines near the wire are almost concentric circles
ii) as we move to the centre of the circle, the concentric circles become larger and larger. Near the centre, these arcs appear as parallel straight lines.
iii) near the centre, the magnetic field becomes almost uniform. So in a current carrying loop, the magnetic field arein the same direction and are very strong at centre.
what is the magnetic field in the middle of current carrying circle
it is 0 because the fiels are opp and equal
what happens when two parallel straight conductors are carrying current
i)in opp direction
ii) in same direction
i) they repel because mag field is in same direction
mag field at centre is very strong coz mag field is additive
ii)they attract because the mag field is equal and opp
mag moment is 0 at centre
what does a strength of electromagnetdepend upon?
i) directly proportional to n nuber of turn
ii) direclty proportional to i magnitude of current
ii)i)inversely proprotional to air gap. lesser air gap more strength
how to make a en electromagnet
i) take 10 iron nails
ii)tightly wound copper wire on it
iii)connect the ends of the wire to the two terminals of the battery with a key.
iv)plug in the key
why is ironc ore better than steel to prepare an electromagnet?
i)steel retains magnetic property and becomes a permanent magnet even when current is switched off. it is becuase stell gets parallel of e-s in effect of curent and remains
ii)however soft iron core loses its magnetic properties when the current is wtiched off and hence mag field is temporary. Iron gets the llel oreintatiin of e-s and goes back to zigzag when current is stopped causing it to cancel the charge and make net 0.
how is the magnetic field in our body used in mri?
Two main organs in the human body where
the magnetic field produced is significant, are the heart and the brain. The magnetic field
inside the body forms the basis of obtaining the images of different body parts. This is
done using a technique called Magnetic Resonance Imaging (MRI). Analysis of these
images helps in medical diagnosis.
is there a magnetic field near our nerve cells
An electric current always produces a magnetic field. Even weak ion currents that
travel along the nerve cells in our body produce magnetic fields. When we touch
something, our nerves carry an electric impulse to the muscles we need to use. This
impulse produces a temporary magnetic field. These fields are very weak and are about
one-billionth of the earth’s magnetic field.
what makes aquatic animals survive? swim in the ocean
aqutic animals have natural lodestone in them, such tiny magnetic field intercepts the earth’s mag field allowing them to go deeper.
what are uses of permanent magnets
microphone,ammeter,voltmeter,geenrator,motor,fridge door
how can permenant magnets be demagnetised
i)heating them
ii)dropping continuously from a reasonable height
iiii)improper storing
iv)hammering
when do we get a force experienced by particles? explain the diff conditions
F=qvBsinθ
the particle must be charged, if q=0 then f=0
the charged particle must be moving with a velcotiy if charged particle is at rest then v=0,then F=0
there must be a definite magnetic field. B must be there, if B=0 then F=0
angle theta is the angle between the direction of the moving charged particle and the direction of magnetic field. If theta=90 then sin90=1, the force is maximum. If theta=0/180, sin0=0 then force =0. the particle must not be parallel nor antiparallel.
a charged particle in an external field experiences a force? where is this used?
This force is used to accelerate charged particles. EX: van de graaf generator, used to bombard and study the atomic nucleus/tv picture tube
