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Describe in words the Kirchoff ’s Junction Rule?

Describe in words the Kirchoff ’s Junction Rule?. Kirchhoff’s Junction Rule The sum of the currents entering a junction must equal the sum of the currents leaving a junction. questions without calculations. What did Hans Christian Oersted discover?.

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Describe in words the Kirchoff ’s Junction Rule?

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  1. Describe in words the Kirchoff’s Junction Rule? Kirchhoff’s Junction Rule The sum of the currents entering a junction must equal the sum of the currents leaving a junction

  2. questions withoutcalculations What did Hans Christian Oersted discover? Oestered discovered that the current in the wire produces a magentic field

  3. MAGNETIC FIELD

  4. An electron travels through a magnetic field, as shown below. The particle’s charge is 1.6 ×10-19 C The particle’s initial velocity is 5 x 106 m/s, and the magnitude of the magnetic field is 0.4 T. What are the magnitude and direction of the force acting on the particle ?

  5. positive charge v B F

  6. The direction of themagnetic field is given by the RighthandRule current (I) in direction of thumb curl fingers in directionof field (B)

  7. Magnetic field due to a long, straight current-carrying wire

  8. The preceding illustration shows current-carrying wire. The current in wire is 1 A. What is the magnetic field at point C, 1 cm from wire. (Give both magnitude and direction.). The permeability of free space, and its value is0=4×10 -7 Tm/A IA=1A C 1cm

  9. ELECTRIC CURRENT

  10. Combining Circuit Elements (Resistors and Capacitors) Two resistors, R1 and R2, are 2  and 4, respectively. Find their resistances when placed in (a) series and (b) parallel. Find the equivalent capacitance when the capacitors are placed in series

  11. Electrical Resistance Resistance: R = rl/A where r: resistivity l:lenght A: cross-sectional area

  12. Capacitance Q -Q E • Capacitance of a parellel-plate arrangement is C=εoA/d where εo is a constant – describes electrical properties of free space εo =8.85x10-12C2/(N·m2) A - area of plate d- the separation between the plates  - dielectric constant A

  13. A 10 m long wire with a diameter of 0.2 mm registers a resistance of 2 . Determine the resistivity of the wire’s component metal. Determine the capacitance of the parallel-plate capacitor. The separation of the plates is 5mm. The plate area is 10-4 m2 , and the capacitor is filled with a material whose dielectric constant is 3.5. The constant εo =8.85x10-12C2/(N·m2)

  14. Electric current What total charge passes by a given point in a circuit carrying 10 A in 1 minute?

  15. REAL BATTERY EMF INTERNAL RESISTANCE A battery has an emf of 6 V and an internal resistance of0.01 . Its terminals are connected to a load resistance of 2  . Find the current in the circuit.

  16. Kirchhoff’s Junction Rule The sum of the currents entering a junction must equal the sum of the currents leaving a junction Kirchhoff’s Loop Rule The sum of voltage drops around a complete circuit loop must equal zero.

  17. Electric Units Emf()and Voltage (V)is measured in VOLTS (V) Electric Current(I) in AMPERES (A) Electric Resistance(R)in OHMS (Ω) Capacitance (C) in FARAD (F) Power (P) in WATT (W)

  18. Therapeutic application of electric current Iontophoresis Ingestion medical substance in tissues

  19. Methods that use Electrolytic Effect of DC Current IONOPHORESIS is a method of an introducing of drugs dissolved in water to the eye, knee, joints, skin .. Point:The method based on the fact that ions with the same charges are repelled. Contrary,the ions with the opposite charges are attracted.

  20. Human Body and Electricity Body is a non-uniform space conductor where an electric current flows according to electric tissue conductivity.Body tissues have diffe-rent resistances (impedances), and therefore different conductances. The highest el. resistance (Impedance) have the fat and bone tissues (R = 40-50 Ω/m) The lowest el. resistance (Impedance) have a blood, liquor, lymphatic fluid (R = 0.8 Ω/m) El. resistance for dry skin is high (R=1000 Ω/m) El. resist. for moistured skin is low (R=50 Ω/m)

  21. Theharmful effect of electricity on a living body depends on Intensity of el.current, on the impedance and the insulation of the body against the ground. Electric shock is caused only by Electric Cu-rent, which is determined both by a Volta-ge and body Resistance.

  22. Ohm’s Law In many materials, the voltage and resistance are connected by Ohm's Law: Ohm’s law is an assertion that the current through a device is always directly proportional to the potential difference applied to the device.

  23. How does Ohm's law relate to physiology? An electrical potential difference(Δ V) , the driving force for electrical current, is therefore analogous to the pressure difference (ΔP) generated by the heart between arteries and veins, which provides the driving force for blood flow. 

  24. How does Ohm's law relate to physiology? We can also apply Ohm's law to the cardiovascular system. Electrical current, a flow of charged particles, is analogous to the flow of blood in the bloodstream. We can therefore draw a direct analogy between Ohm's law and flow in the cardiovascular system:

  25. Write a classification of electromagnetic waves from lowest to highest frequency. question withoutcalculations

  26. questions withoutcalculations Which kind of wave a) has highest frequency ……………. b) is used in MRI ………..

  27. l x f = c Find the wavelength (in vacuum) for red light (f=4×1014 Hz ).

  28. What is Magnetic resonance imaging (MRI)? is a medical imaging techniquethat uses a magnetic field and pulses of radio wave energy to make pictures of organs and structures inside the body.

  29. True or False • X rays are made of the same “stuff” as visible light. They are both forms of “electromagnetic radiation”. • X rays can damage healthy tissues. • PET scanning poses no risk to patient health. Doctors can use them as often as they like.

  30. Doctors often need to look inside our bodies without cutting them open…. Some you may have heard of… CTscans…..MRIscans And new ones you may not have heard of yet…. PET scans…..MEG are essential in the development of many scanning technologies

  31. Taking “X rays” The patient is placed in front of a source of X RAYS X ray Tube A photo graphic plate is placed on the other side of the patient Most of the X rays pass through the patient’s body…….

  32. X-rays are absorbed by bone but can pass through skin and soft tissue Photographic plate bone X rays that are absorbed in the photographic plate cause chemical changes. These show as darkened areas when the plate is developed. Soft tissue

  33. X-rays are also partly absorbed by some tissues in the body this creates a more subtle picture. Photographic plate bone Soft tissue

  34. Advantages of Basic X ray Imaging • X rays are easy to produce • X ray machines are relatively cheap • In controlled doses X ray images are safe to the patient

  35. Disadvantages of X ray Imaging • In large doses X rays can be harmful to health • Images are only “shadow prints” in one “plane”…..no 3D information • Imaging of soft tissues and organs is not always very detailed.

  36. In short…. CT scanners are complex X ray machines attached to very clever computers using complicated mathematics to build up images of our insides.

  37. The patient is placed on a bed The scanner (X ray machine) is the shape of a ring The patient is slowly moved through the ring as the scan takes place…

  38. Looking end on…. X ray tube X Rays are produced in an X ray tube, pass through the patient and are detected by the detector Patient The scanner rotates the X ray tube and detector so the patient is scanned from all angles X ray detector

  39. There are no photographic plates in CT scanners. All images are created by computers using the information they receive from the x-ray detector The image produced is like a “slice” through the body. ribs spine

  40. Advantages of CT scans • Images are like “slices” • Compared other scanners (MRI and PET) CT machines are quite cheap.

  41. Disadvantages of CT • Still use X rays that can damage healthy tissues (in large doses). • Imaging of soft tissues is improved but still not always as detailed as doctors require.

  42. MRI What do the letters stand for? M……….. Magnetic R………… Resonance I…………. Imaging MRI scanners do not use X rays.

  43. MRI Explained... Your science studies have shown you that your body is made up of living cells… Which are made up of molecules … Which are made up of atoms

  44. The simplest atom is… 1 electron Hydrogen 1 proton It’s nucleus contains just one proton

  45. In the 1940’s physicists discovered that the nuclei of some atoms have a property called “SPIN”… ….Like a wobbling spinning top. This causes the nucleus act like a tiny magnet…. N S

  46. In the absence of a strong magnetic field, the spins are oriented randomly. Thus, there is no net magnetization (M).

  47. In a magnetic field, protons can take either high- or low-energy states

  48. Basic Quantum Theory • Radiation is absorbed • Energy increases • Radiation is emitted • Energy decreases Lower Higher

  49. This tiny pulse of radio waves that can be detected and analysed. The timing, and the energy of these signals, reveals information about the Hydrogen atoms and what types of molecules they are attached to.

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