magnetism Flashcards
magnetic field line?
imaginary path in which the magnetic north monopole travels in the presence of an external magnetic field
monopole cannot exist
properties of mfl
- direction of mfl indicates the direction of mf at that point
- density of mfl is an indicator of the mfs in that region
- mfls form closed loops
- mfls appear to emerge from the north pole and appear to terminate at the south pole
- two field lines never ever intersect each other
if they intersect at a point, the magnetic north monopole will have two paths to travel in at the point of intersection. since this is not possible, the assumption that two field lines intersect is wrong.
root cause of magnetic field
current
static charge creates an electric field
flowing charge creates a mf also
direction of mf generated by straight current carrying wire
right hand thumb/grip rule
to determine direction of mf generated by straight current carrying wire
thumb = direction of conventional current
four fingers = direction of mf
.
anything coming of page
north
x
anything going into the page
south
direction of mf generated by current carrying loop
right hand thumb/grip rule reversed
to determine direction of mf generated by a current carrying loop
four fingers = direction of conventional current
thumb = direction of mf
factors affecting strength of mf generated by current carrying solenoid
- no. of coils
- current
- no. of coils per unit length
- material of the core
- distance from solenoid
each coil’s mf adds to the overall field, creating a stronger, more concentrated mf
magnetic force acting on a straight current carrying wire due to an external mf
F=BIL(sintheta)
- B = tesla, strength of the external mf
- I = current flowing through the straight current carrying wire
- L = length of the wire present within the external magnetic field
no need of sin theta at the end
direction of the magnetic force acting on a straight current carrying wire due to an external mf
fleming’s left hand rule
or right hand jhapad rule
index = direction of external mf
middle = direction of conventional current
thumb = direction of the force acting on the wire
force acting on a moving charge due to an external mf
F=Bqv
- B = strength of external mf (tesla)
- q = charge on the movign charge
- v = speed of the moving charge
faraday’s law of electromagnetic induction
induced emf is directly proportional to the negative rate of change in magnetic flux linkage
V=-∆Φ/∆t
V=∆(NBAcosθ)/∆t
magnetic flux (linkage)
Φ=(N)BAcosθ
- (N) = number of coils
- B = strength of external mf
- A = cross-sectional area of loop
Wb
θ = angle formed bw direction of external mf and perpendicular to A
magnetic flux
measure of number of field lines passing parallel to the perpendicular to the area of cross-section
