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ACCELERATING ELECTRONS Will produce alternating electric and magnetic fields (No wires necessary!)

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Presentation on theme: "ACCELERATING ELECTRONS Will produce alternating electric and magnetic fields (No wires necessary!)"— Presentation transcript:

1 ACCELERATING ELECTRONS Will produce alternating electric and magnetic fields (No wires necessary!)

2 Robert Millikan Oil drop experiment Used to determine the charge on an electron. Static force is equal to gravitational force so drop is suspended. Eq = mg q = mg E

3 J.J. Thomson Determined the charge to mass ratio of the electron. (q/m)

4 Frederick Soddy Used the idea of charge to mass ratio show that isotopes exist. Isotopes are atoms of an element with the same chemical properties but different atomic mass.

5 Mass Spectrometer-to determine the concentration of isotopes in an element Charged particles are deflected differently due to their mass.

6 Cathode Ray Tubes- Deflect electron beams through a magnetic coil or charged plates. This hits the back of a screen covered with phosphors that give off light.

7 Wilhelm Röntgen X-ray- High energy, high frequency wave emitted by some cathode ray tubes. Original x-rays were difficult to control and often caused severe skin burns. He varied the electric potential to control the x-ray and reduce burns. Lead screen is used to reduce cell damage.

8 Television (CRT) Electric circuit scans the screen 30 times/sec.

9 Primary colors (red, blue, green) make up what is seen on the screen.

10 LCD-liquid crystal display Plasma Screen

11 Radio- Uses electromagnetic waves to transmit and receive signals AM radio- amplitude variations 535-1705 kHz FM radio-frequency variations. 88-108 MHz

12 Cell Phones Operate at 825-900 MHz. High frequency means there is a stronger signal and a shorter antenna can be used.

13 Radio Signals Other uses: toys, garage door openers, baby monitors, satellites, police radio, GPS, weather

14 EMF Electromotive Force The potential difference produced by electromagnetic induction

15 EMF= V =BLv V- potential difference(V) L- length of wire(m) B- Magnetic Field (Tesla) v- velocity(m/s) Ex: An antenna on a remote control car is 0.20m long and is traveling at 7.0m/s through a magnetic field of 8x10 -2 Tesla. What EMF is induced in the antenna? V= BLv V= 8x10 -2 T(0.20m)(7.0m/s) V= 0.112V


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