From Ideas of Implemenation Essay

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Cathode Rays Electric Fields • Like charges Repel • Unlike charges attract • Charge surrounded by electric field - field exerts force on other charges placed in the filed • Positive moves to negative Strength of electric field at a point Force that a +1 Coulomb charge would experience if placed at point • Each point in field has : • Strength • Direction • Density of lines related to strength of field • Lines close together - strong field • Parallel plates - electric field in uniform • F - Force (from electric field) • q - Force on charge (coulombs). • E - Field strength F = qE • V - Voltage • d - Distance (m) (between parallel plates) • E - Electric field strength (NC-1 ) E= Unit 3 From Ideas to Implementation Page 1 Magnetic Fields • • • • Stationary charge in magnetic field - experience no force Charges moved any angle to the field - experience force Max force - when perpendicular Min force - when parallel Right Hand Gives direction of force on a moving Palm Rule positive charge or current carrying wire in a magnetic field • Strength of force on charge moving in mag field: ○ F - Force (Newton's) ○ q - Charge in coulombs ○ v - Velocity ○ B - Magnetic field strength (tesla) ○ sinθ - Angle between mag field and velocity of charge • If charge enters field .90 Degrees - helical path • Break up components: ○ Perpendicular - circular motion ○ Parallel - continue unchanged Circular motion move at constant speed parallel to field F = qvB sinθ Unit 3 From Ideas to Implementation Page 2 History of Cathode Rays and Cathode Ray Tubes • When high voltage placed across a gas in a vessel at low pressure - gas conducts electricity • Studied since 19th Century • Free electrons move towards anode (positive) • Positive Ions move towards cathode (negative) • When electrons collide with atoms in tube ○ Atoms become excited ○ Release light ○ Gas

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