1 John Parkinson ©

2 THE AURORA The Aurora Borealis, the Northern Lights and the Aurora Australis, the Southern lights are phenomena resulting from the interaction between Solar Wind and the Earth’s magnetic field.

3 N S Lines of magnetic flux, Φ Magnetic flux density, B, measures the strength of the magnetic field. B = number of lines of flux per square metre UNITS are Webers per square metre Wb m -2 or TESLAS (T) B IS A VECTOR QUANTITY

4 N S Lines of magnetic flux, Φ A Total magnetic flux through area A is given by: Φ = B A webers, when the area is perpendicular to the field A θ Φ = B A sinθ

5 geographic north magnetic north s N

Professor Oersted was demonstrating an experiment for students when he accidentally discovered that a compass needle moved when it was close to a wire connected to a battery. Professor Hans Christian Oersted

7 B I

8 I B

9 RIGHT HAND GRIP RULE: I

10 current outwards current inwards r B -

11 length l I N turns In the middle at the end

12 N S Interaction between a magnet and the field due to a current N S

13 N S F

14 FLEMING’S LEFT HAND MOTOR RULE F OREFINGER = F IELD THU M B = M OTION SE C OND FINGER = C URRENT

15 FLEMING’S LEFT HAND MOTOR RULE F OREFINGER = F IELD THU M B = M OTION SE C OND FINGER = C URRENT

16 N S I B F F = B I l Where l = length of conductor in the field

17 SN HAIR SPRINGS CONTROL MOVEMENT AND ALLOW CURRENT TO ENTER AND LEAVE THE COIL RADIAL SOFT IRON POLE PIECES COIL PERMANENT MAGNET MOVING COIL METER SOFT IRON CYLINDER

18 SN + +

19 N A B D C I S brushes EVERY TIME THE COIL PASSES THROUGH THE VERTICAL POSITION, THE COMMUTATOR REVERSES THE CURENT IN THE COIL, IN ORDER TO SUSTAIN THE ROTATION DC MOTOR C A B SN D I Split ring commutator

20 LOUDSPEAKER N S N Solenoid on paper cone is forced to vibrate - left hand rule magnet S N NN N AC signal coil

21

22 Force experienced by a charged particle (charge Q) moving with a velocity, v in a magnetic field of Flux density, B + Q B I A B l Particle travels l metres from A to B in t seconds F F = B I l but F = B Q v

23 + I F F THE FORCE IS ALWAYS PERPENDICULAR TO THE MOTION THE PARTICLE MUST MOVE ALONG AN ARC OF A CIRCLE +

24 Frequency of Rotation, f x x x x x x x x x x x x x x x x x x x x x x x x B inwards + The frequency is independent of the radius and the velocity This is the principle of the CYCLOTRON

25 High frequency square wave to accelerate charge across the gap CYCLOTRON + High frequency square wave