Master the High School and AP Physics curriculum

First time --- guaranteed expertise (or money back) @ students seeking PHYSICS | MAGNETISM | ALTERNATING CURRENT|Wave Optics-IB Diploma SL/HL | Cambridge (AS, A LEVEL - Further),CBSE

Bonus -RAY optics

US/INTERNATIONAL-11TH AND 12TH

This Course will make students confident in working with information and ideas – their own and those of others • responsible for themselves, responsive to and respectful of others • reflective as learners, developing their ability to learn • innovative and equipped for new and future challenges • engaged intellectually and socially, ready to make a difference

Coverage :

• Magnetic fields

• Magnetic force

Electromagnetic induction

(HL ONLY)

• Electromotive force (emf)

• Magnetic flux and magnetic flux linkage

• Faraday's law of induction

• Lenz's law

How to:

Describe the forces between magnets, and between magnets and magnetic materials • Give an account of induced magnetism • Distinguish between magnetic and non-magnetic materials • Describe methods of magnetisation, to include stroking with a magnet, use of direct current (d.c.) in a coil and hammering in a magnetic field • Draw the pattern of magnetic field lines around a bar magnet • Describe an experiment to identify the pattern of magnetic field lines, including the direction • Distinguish between the magnetic properties of soft iron and steel • Distinguish between the design and use of permanent magnets and electromagnets

Explain that magnetic forces are due to interactions between magnetic fields • Describe methods of demagnetisation, to include hammering, heating and use of alternating current (a.c.) in a coil

Electromagnetic induction Core • Show understanding that a conductor moving across a magnetic field or a changing magnetic field linking with a conductor can induce an e.m.f. in the conductor • Describe an experiment to demonstrate electromagnetic induction • State the factors affecting the magnitude of an induced e.m.f.

Show understanding that the direction of an induced e.m.f. opposes the change causing it • State and use the relative directions of force, field and induced current

a.c. generator Core • Distinguish between d.c. and a.c

Describe and explain a rotating-coil generator and the use of slip rings • Sketch a graph of voltage output against time for a simple a.c. generator • Relate the position of the generator coil to the peaks and zeros of the voltage output

4.6.3 Transformer Core • Describe the construction of a basic transformer with a soft-iron core, as used for voltage transformations • Recall and use the equation (Vp /Vs ) = (Np /Ns ) • Understand the terms step-up and step-down • Describe the use of the transformer in highvoltage transmission of electricity • Give the advantages of high-voltage transmission

• Describe the principle of operation of a transformer • Recall and use the equation IpVp = IsVs (for 100% efficiency) • Explain why power losses in cables are lower when the voltage is high

4.6.4 The magnetic effect of a current Core • Describe the pattern of the magnetic field (including direction) due to currents in straight wires and in solenoids • Describe applications of the magnetic effect of current, including the action of a relay

State the qualitative variation of the strength of the magnetic field over salient parts of the pattern • State that the direction of a magnetic field line at a point is the direction of the force on the N pole of a magnet at that point • Describe the effect on the magnetic field of changing the magnitude and direction of the current

4.6.5 Force on a current-carrying conductor Core • Describe an experiment to show that a force acts on a current-carrying conductor in a magnetic field, including the effect of reversing: – the current – the direction of the field

Supplement • State and use the relative directions of force, field and current • Describe an experiment to show the corresponding force on beams of charged particles

4.6.6 d.c. motor Core • State that a current-carrying coil in a magnetic field experiences a turning effect and that the effect is increased by: – increasing the number of turns on the coil – increasing the current – increasing the strength of the magnetic field

Supplement • Relate this turning effect to the action of an electric motor including the action of a split-ring commutator

Magnetic Dipole

Magnetic dipole is an arrangement of two unlike magnetic poles of equal pole strength separated by a very small distance, e.g., a small bar magnet, a magnetic needle, a current carrying loop etc.

Magnetic Dipole Moment

The product of the distance (2 l) between the two poles and the pole strength of either pole is called magnetic dipole moment.

Magnetic dipole moment

M = m (2 l)

Its SI unit is ‘joule/tesla’ or ‘ampere-metre2‘.

Its direction is from south pole towards north pole.

Magnetic Field Due to a Magnetic Dipole

(1) On Axial Line

If r > > l, then

B = μo / 4 π 2M / r3

(ii) On Equatorial Line

B = μo / 4 π M / (r2 + l2)3 / 2

If r > > l, then

B = μo / 4 π 2M / r3

Torque Acting on a Magnetic Dipole

When a Magnetic Dipole (M) is placed in a uniform magnetic field (B), then a Torque acts on it, Which is given by

τ = M * B

or τ = MB sin θ

Where θ is angle between the dipole axis and magnetic field.

Potential Energy of a Magnetic Dipole in a Uniform Magnetic Field

The work done in rotating the dipole against the action of the torque is stored as potential energy of the dipole.

Potential Energy, U = W = – MB cos θ = – M . B

Current Carrying Loop

A current carrying loop behaves as a magnetic dipole. If we look the upper face of the loop and current is flowing anti-clockwise,then it has a north polarity and if current is flowing clockwise.then it has a south polarity.

Magnetic dipole moment of a current carrying loop is given by

M = IA

For N such turns M = NIA

Where I = current and A = area of cross-section of the coil.

Gauss’s Law in Magnetism

Surface integral of magnetic field over any closed or open surface is always m.

This law tells that the net magnetic flux through any surface is always zero.

[When in an atom any electron revolve in an orbit it is equivalent to a current loop. Therefore, atom behaves as a magnetic dipole].

Magnetic Moment of an Atom

Magnetic moment of an atom M = 1 / 2 eωr2

where e = charge on an electron, ω = angular velocity of electron and r = radius of orbit.

or M = n eh / 4πm

where h = Planck’s constant and m ~ mass of an electron and eh / 4πm = μB, called Bohr magneton and its value is 9.27 * 10-24 A-m2.

Earth’s Magnetism

Earth is a huge magnet. There are three components of earth’s magnetism

(i) Magnetic Declination (θ) The smaller angle subtended between the magnetic meridian and geographic meridian is called magnetic declination.

(ii) Magnetic Inclination or Magnetic Dip (δ) The smaller angle sub tended between the magnetic axis and horizontal is called magnetic inclination on magnetic dip.

Entire Alternating Current included as bonus lecture.