Magnetism and Electromagnetism Notes by Sir Waqar Hussain
Important Easy Notes of Physics of Chapter No. 14: Magnetism and Electromagnetism written by Professor Mr. Waqar Hussain Suib. These notes are very helpful in the preparation of Physics for students of the 12th class and these are according to the paper patterns of all Sindh Book Boards.
Summary and Contents:
Topics which are discussed in the notes are given below:
- Definition of Magnet
- Definition of Magnetic Field
- Definition of Magnetic Force
- Definition of Magnetic Lines of Force
- Definition of Properties of Magnetic Lines of Force
- Definition of Magnetic Field of a Straight Wire
- Force on Charge Particle in a Uniform Magnetic Field with Mathematical Expression
- Trajectory of a charged particle moving in a uniform magnetic field
- Force on a current carrying conductor in a uniform magnetic field
- Torque on a Current Carrying Coil in a Uniform Magnetic Field
- Definition of Magnetic Flux
- Definition of Mathematical Definition with its Notation and formula
- Definition of Magnetic Flux Density with its Notation and formula
- J.J Thomson Experiment for charge to mass ratio of
electron with Significance, Experimental Setup and working, Calculations, Calculation for velocity, Calculation for Radius
- State and Explain Biot-Savart Law with its Mathematical Expression
- State and Explain Ampere’s Law with its Mathematical Expression'
- Application of Ampere’s Law
- Determination of “B” Inside a Long Solenoid'
- To Determine the Line Integral of Magnetic Induction
- To Determine the Total Current Passes Through Amperian Loop
- Definition of Toroidal Field and also Explain it.
- Define and Explain Electromagnetic Induction with Faraday’s Law and Lenz’s Law
- Definition of Mutual-Induction and also Explain it with Mathematical Expression
- Definition of Self-Induction and also Explain it with Mathematical Expression
- Definition of Motional E.M.F
- Definition of Electromechanical Device
- Definition of Electric Motor
- Definition of Generator
- Definition of Alternating Current Generator (Dynamo) and also Explain it with Working
- Expression for EMF of an AC generator
- Expression For Maximum emf
- State and Explain Transformer with its Construction and Working
- Definition of Efficiency of Transformer
- Definition of Step Up Transformer
- Definition of Step Down Transformer
- A toroidal coil has 300 turns and its mean radius 12cm. Calculate the magnetic field of induction
‘B’ inside the coil when a current of 5 amperes passes through it.
- Current of 2 amperes passes through an inductive circuit. What is the self-inductance of
the circuit if the current falls to zero in 0.1 seconds? The average value of induced e.m.f.
is 20 volts.
- A train is moving directly towards south with a uniform speed of 10m/s, if the vertical
component of the earth’s magnetic field induction is 5.4x10–5 Tesla. Compute the e.m.f. induced
in the axle 1.2m long.
- An electron having a speed of 1.6x106 m/s is moving along a circle of radius 1.82x10–6m entering
perpendicularly in a uniform magnetic field. Find the value of magnetic field.
- A solenoid of diameter 5.0cm is 25cm long and has 250 turns. If the current flowing in it is 5
amperes, find B inside the solenoid.
- Find the current required to produce a field of induction B = 2.51x 10–3 web/m2 in a 50cm long
solenoid having 4000 turns of wire.
- A current of 2 amperes is passing through a solenoid. If the solenoid has 24 turns per cm of its
length, find the value of B.
- A transformer has 1000 turns in its primary coil. If the input voltage of the transformer is 200
volts, what should be the number of turns of the secondary coil to obtain an output of 6.0 volts?
- A 10eV electron is moving in a circular orbit in a uniform magnetic field of strength 10-4weber/m2
.
Calculate the radius of the circular path.
- A coil having an area of cross section 0.05m2 and number of turns 100 is placed perpendicular to
the magnetic field of induction 0.08 weber/m2
. How much e.m.f. will be induced in it if the field
is reduced to 0.02 weber/m2
in 0.01 seconds?
- A solenoid 25cm long has a cross-section of 5 square cm with 250 numbers of turns on it. If a
current if 5 amperes is passed through it, find “B” in it.
- An electron is moving along a circle of radius 1.8 x 10–7m. Calculate the speed of the electron on
entering perpendicularly in a uniform magnetic field of 5.0 Tesla.
- A coil of 100 turns and area (4cm x 2cm) is placed in a uniform magnetic field of 0.45 T. The coil
carries a current of 1.5 amperes. Calculate the torque on the coil when the plan is at 60° with B.
- An airplane is flying in a region where the vertical component of earth’s magnetic field is
3.2x10–4T. If the wingspan of the airplane is 50m and its velocity is 360 km/hour, find the
potential difference between the tips of the wing of airplane.
- An alpha particles are accelerated from rest at a P.D. of 1 KV. They then enter a magnetic field
B=0.2T perpendicular to their direction. Calculate the radius.
Given m = 6.68 x 10–27 kg & q = 2e.
- A solenoid 20 cm long has three layers of windings of 300 turns each. If a current of 3 amperes is
passed through it, find the value of the magnetic field of Induction.
- A 500 turn coil in A.C. Generator having an area of 1000 cm2
rotates in a magnetic field of value
50 Tesla. In order to generate 220 volts maximum, how fast is the coil to be rotated? Express
your answer in terms of the number of revolutions per second.
- A 10eV electron is moving in a circular orbit in a uniform magnetic field of strength 10-4
weber/m2
; calculate the radius of the circular path.
- A transformer has 1000 turns in the primary coil. If the input voltage of the transformer is 200
volts, what should be the number of turns of the secondary coil to obtain an output of 6.0 volts?
- What will be the mutual inductance of two coils when the change of a current of a 3 amperes in
one coil produces the change of flux of 6 x 10–4 Weber in the second coil having 2000 turns?
- An electron is accelerated by the potential difference of 1000 volts. It then enters into a uniform
magnetic field of induction B = 2.5, weber/m2 at an angle of 45° with the direction of the field,
find the value of the path described by the electron.
- A long solenoid is wound with 10 turns per cm and carries a current of 10 amperes; find the
magnetic flux density within it.
- An e.m.f. of 45 milli-volts is induced in a coil of 500 turns, when the current in a neighboring coil
changes from 10 amperes to 14 amperes in 0.2 seconds.
a) What is the Mutual Inductance of the coils?
b) What is the rate of change of flux in the second coil?
- The current in a coil of 325 turns is changed from zero to 6.32 amperes thereby producing a flux
of 8.46 x 10–4 Webers. What is the self-inductance of the coil?
- Calculate the speed of an electron entering perpendicularly in a uniform magnetic field of 5.0
w/m2 which moves along a circle of radius 1.8 x 10–6 m in the field.
- A coil of 50 turns is wound on an ivory frame 3cm x 6 cm which rotates in a magnetic field of
induction B = 2 web/m2
. What will be the torque acting on it if a current of 5 amp passes
through it and the plane of the coil makes an angle of 45° with the field.
- How fast must a proton of mass 1.67 x 10–27 kg be moving if it is to follow a circular path of
radius 2.0 cm in a magnetic field of 0.7 Tesla? (1.34 x 106 m/sec)
Q.6. (d) The current in a coil of 500 turns is changed from zero to 5.43 amps. Thereby producing a
magnetic flux of 8.52 x 10–4 Webers. What is the Self-Inductance of the coil?
- A proton accelerated through 1000 volts is projected normal to a 0.25 Tesla magnetic field.
Calculate the following:
a) The Kinetic energy of the proton on entering the magnetic field.
b) The radius of the circular path of the proton
- A step-down transformer having 4000 turns in primary is used to convert 4400 volts to 220
volts. The efficiency of the transformer is 90% and 9KWatt output is required. Determine the
Input power, the Number of turns in the secondary coil and the current in the primary and
secondary coils?
- A long solenoid is wound with 35 turns in 10cm and carries a current of 10A. Find the magnetic
field in it.
- An airplane is flying in a region where the vertical component of earth’s magnetic field is
3.2x10–4T. If the wingspan of the airplane is 50m and its velocity is 360 km/hour, find the
potential difference between the tips of the wing of airplane.
- A step-down transformer reduces 1100V to 220V. The power output is 12.5KW and overall
efficiency of the transformer is 90%. The primary winding has 1000 turns. How many turns do
the secondary have? What is the power input? What is the current in each coil?
- A pair of adjacent coil has a mutual inductance of 850mH. If the current in the primary coil
changes from 0 to 20A in 0.1 sec; what is the change in the magnetic flux in the secondary coil of
800 turns?
- Find the current required to produce a field of induction B = 2.512 x 10–3 T in a 50 cm long
solenoid having 4000 turns of wire. (µo = 4π x 10 –7Wb/A-m
- An alternating current Generator operating at 50 Hz has a coil of 200 turns, while the coil has
an area of 120cm2
. Calculate the magnetic field intensity applied to rotate the coil to produce
the maximum voltage of 240V.
- The inner and the outer diameters of the toroid are 22cm and 26cm. If a current of 5.0 amp is
passed which produces 0.025 tesla flux density inside the core, find the approximate length of
the wire wound on the toroid. (µo = 4π x 10 –7Wb/A-m).
- Find the current required to produce a field of induction B = 2.512 x 10–3 T in a 50 cm long
solenoid having 4000 turns of wire. (µo = 4π x 10 –7Wb/A-m).
- An alternating current generator operates in at 79 Hz the area of coil is 500 cm2
. Calculate the
number of turns in the coil when a magnetic field of induction 0.06 web/m2 produces a
maximum potential difference of 149 V.
- An iron core of solenoid 500 turns has a cross section of 5 cm2
. A current of 2.3 A passing
through produces of flux of B = 0.53 T. How large an e.m.f is induced in it, if the current is turned
off in 0.1 second? What is the self-inductance of the solenoid?
- An e.m.f. of 45 milli-volts is induced in a coil of 500 turns, when the current in a
neighboring coil changes from 15 amperes to 4 amperes in 0.2 seconds.
a) What is the Mutual Inductance of the coils?
b) What is the rate of change of flux in the second coil?