1 / 23

ELECTROMAGNETISM NCEA LEVEL 2 PHYSICS

ELECTROMAGNETISM NCEA LEVEL 2 PHYSICS. Magnets and fields Mag fields and current Right hand grip rule Solenoids Motor Effect DC Motor Force on a charge Induction. geographic north. geographic north. s. magnetic north. N. MAGNETS AND FIELDS. N. S.

lang
Download Presentation

ELECTROMAGNETISM NCEA LEVEL 2 PHYSICS

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. ELECTROMAGNETISM NCEA LEVEL 2 PHYSICS • Magnets and fields • Mag fields and current • Right hand grip rule • Solenoids • Motor Effect • DC Motor • Force on a charge • Induction

  2. geographic north geographic north s magnetic north N MAGNETS AND FIELDS

  3. N S Magnetic field lines ALWAYSrun north to south. The number of magnetic field lines denotes the strength of the magnetic field (B). The more lines the stronger the magnet B = number of field lines in units called Tesla (T) after Nikoli Tesla

  4. MAG FIELDS AND CURRENT 1820 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

  5. I Oersted noticed that if the current was running in one direction the red part of the needle pointed toward the wire. B

  6. I However if the current flowed in the opposite direction then the red part of the needle pointed way from the wire B

  7. I RH GRIP RULE From this observation a rule was developed Thumb = direction of current. Fingers = direction of mag field lines RIGHT HAND GRIP RULE:

  8. - current inwards current outwards Complete exercises from Page 180 – 181 Rutter Current is coming out of the page Current going into the page Use thumb and fingers of right hand grip rule to work out direction of field.

  9. SOLENOIDS How do we increase the magnetic field generated by the current? Answer: Use more wires This led to the production of the SOLENOID 3 things effect size of magnetic field More current More wires Iron core inserted into coil This combined the magnetic field produced in each wire together producing a larger field

  10. length l The field lines of each wire interact to increase the overall strength of the field. Again use thumb and fingers of the right hand grip rule to calculate which way the field runs. NORTH always has field lines coming out of the solenoid. I Do Exercise Page 182 Rutter

  11. What happens if two magnetic fields interact? MOTOR EFFECT Answer: Unbalanced forces are produced Hang on unbalanced force must produce motion. Newton told us this! F=ma Can we get things to move by using two magnetic fields? Answer: Of course we can

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

  13. F N S The interaction of 2 fields. One from the magnet and one from the current carrying wire interact. Where they are going in the same direction they add together in strength. Where they go in opposite directions they cancel out. A force is then applied in the direction of the greatest force. In this case upwards.

  14. RIGHT HAND SLAP RULE How do I know which way the force is acting? Palm = Force direction Try the exercises on page 183 – 184 Rutter Fingers = field direction Thumb = I direction Right Hand Slap Rule

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

  16. How to build a simple motor Now try pages 185 – 8 Rutter How big is the force? This can be calculated using the following equation: F = BILsin Note: F = 0 Where: F = size of the force (N) B = magnetic field strength (T) I = current (A)  = angle made between two mag fields F = max

  17. FORCE ON A CHARGE We have two types of charges: Positive and negative Two equations can be utilised to determine the force acting on each charge Thus we use different slap rules for each when a charge enters a magnetic field Positive = RH slap rule Negative = LH slap rule F = Bvq Note: If the field is large enough the charge will travel in a complete circle. F= mv2/r can be used F = Bev Where: B = mag field strength (T) v = velocity (ms-1) q = charge (C) e = charge of electron (C)

  18. I Charged particle moving through a magnetic field THE FORCE IS ALWAYS PERPENDICULAR TO THE MOTION F F THE PARTICLE MUST MOVE ALONG AN ARC OF A CIRCLE Try Pages 188 – 190 Rutter

  19. ELECTROMAGNETIC INDUCTION If using electricity and magnetism can generate movement can it work the other way? ANS: Yes, we call it a generator and it works by electromagnetic induction So what is different? ANS: If we change the movement of charge to kinetic movement then the charges are still moving and so a magnetic field is still generated. This means two sets of fields will interact. This means a force will be produced which acts on the only thing that can move, the charge along the wire. Demo of electromag induction

  20. Hey, Mr Lees how much voltage is generated when a magnet moves through a coil? The variables that are involved are: Size of the magnets magnetic field (B) Speed of movement (v) Amount of wire (l) This results in: V = Bvl Where: V = Voltage (V) B = magnetic field strength (T) l = length of wire (m)

  21. The major use of this phenomenon is in hydro-electric dams in the production of electricity. BENMORE DAM NZ How a hydroelectric dam uses induction to make electricity?

  22. OPEN ENDED ESSAY QUESTION Use the diagram opposite to help you describe how New Zealanders have embraced the Physics principles of “Electromagnetism” to generate electricity from water? Try Pages 190 – 193 Rutter

  23. IDEAS THAT CAN BE USED FOR THIS QUESTION The Solenoid Induction Inside a generator Water Height

More Related