M field

Question 1

definition of 1 tesla

Answer 1

flux density that exert a force of 1N on 1m of wire carrying 1 A(amp),B=F/IL

Question 2

condition for resultant force acting on a charged particle moving in the magnetic field

Answer 2

field line is perpendicular to velocity

Question 3

path of the charge entering the field

Answer 3

circular

Question 4

what is the work done when charge entering the M field

Answer 4

zero

Question 5

Direction of acceleration of the charge when entering the field is

Answer 5

towards the centre of circle (F=mv^2/r)

Question 6

speed of the charged particle in the field

Answer 6

constant

Question 7

what is cyclotron

Answer 7

charged particle accelerator that contains semi-circular electrodes “Dees”, strong uniform magnetic field and alternating electric field

Question 8

where is the source of protons in cyclotron

Answer 8

centre of the circle

Question 9

briefly explain how happens when the particle enter the dee

Answer 9

-source of charged particle at the centre
-magnetic field applied perpendicular to the path
-magnetic force acting perpendicular to the path and the field
-moving in circular path in the Dees

Question 10

when particle crossing the gap between the Dees

Answer 10

-electric field is applied
-alternating voltage and field accelerates the particle due to electric force
-moving in higher speed and larger radius in the follow path in the Dees

Question 11

role of magnetic field in cyclotron

Answer 11

To supply the centripetal force needed to keep the particles moving in circular motion

Question 12

role of electric field

Answer 12

To accelerate the particles between the Dees

Question 13

formula of the radius of the protons path

Answer 13

r=mv/BQ

Question 14

formula of time taken for the proton to travel through one dee(semi-circle)

Answer 14

t=m(pi)/BQ

Question 15

what factors affect the final velocity

Answer 15

radius of the dee and magnetic field strength

Question 16

does time taken for a particle moving around the Dees depend on speed of the charge

Answer 16

no

Question 17

what can we say about the time period of the AC voltage in cyclotron

Answer 17

constant as particle moving in constant speed in the Dees

Question 18

In mass spectrometer what conditions will the ions pass through the E and M fields in a straight line

Answer 18

forces by the two fields acting in opposite direction and are equal (EQ=BQv)

Question 19

describe the process of electromagnetic induction

Answer 19

inducing emf(p.d.) in a conductor when there is a relative motion between the magnetic field and a charge

Question 20

define flux

Answer 20

total amount of magnetic field lines(magnetic flux)in a given area, flux=BA

Question 21

define flux linkage

Answer 21

amount of magnetic flux in all the loops added together

Question 22

when is the flux/flux linkage at its min and max

Answer 22

max when the plane of area is perpendicular to the field lines(cut the field lines)
min when the plane is parallel the field lines (does not cut the field lines)

Question 23

formula of flux linkage

Answer 23

flux linkage=N(/BA)fluxcos (theta), where theta is the angle between the axis of the coil and the flux

Question 24

factors that increase the emf induced in a coil

Answer 24

-increasing the magnetic field strength
-increasing speed of motion of the magnet
-adding more turns

Question 25

factors that decrease the emf in a wire

Answer 25

-decrease the length of wire -decrease the strength of the magnet - reduce the speed of motion of the magnet

Question 26

what does Faradays law suggest

Answer 26

that the magnitude of induced emf is proportional to the rate of change in magnetic flux linkage

Question 27

what does Lenz's law suggest

Answer 27

the direction of emf induced will oppose the change that causing the induced emf

Question 28

formula of induced emf in a coil rotating uniformly in a magnetic field

Answer 28

ε=BANωsin ωt

Question 29

equation for induced emf for a conductor of 1 turn

Answer 29

ε=Blv

Question 30

what is time base

Answer 30

how many seconds in each division represent

Question 31

what does it mean when a vertical straight line shown on the oscilloscope

Answer 31

time base is turned off and only voltage is shown

Question 32

what does it mean when a horizontal straight line shown on the oscilloscope

Answer 32

dc supply as voltage remains constant

Question 33

shape of graph for ac current/voltage

Answer 33

sinusoidal

Question 34

how can p.d. cross the two coils in a transformer

Answer 34

-alternating current and voltage in the primary coil -this causes change in magnetic field therefore change in magnetic flux linkage inside the iron core - emf is induced in the secondary coil

Question 35

what is the role of iron core

Answer 35

-increase the strength of magnetic field -channel the magnetic field through the secondary coil

Question 36

what happen when secondary coil has more turns

Answer 36

increased voltage output

Question 37

describe eddy current

Answer 37

-eddy current is induced in the core -as magnetic field is changing -inducing an emf is in the core -this produces a field that oppose the field in the core and reduces its strength

Question 38

causes of insufficiencies in transformers

Answer 38

-eddy current -hysteresis-->iron ions rotate, causes friction -wire power loss P=I^2R

Question 39

ways to reduce insufficiencies

Answer 39

-use soft iron to reduce hysteresis -use thicker wire to reduce resistance -laminating the core