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Electric field patterns An electric field pattern can be produced by using semolina grains sprinkled on oil between + & - high voltage metal conductors The line of force or Field line direction is the path a small positive test charge would follow if free to move + Electric field patterns An electric field pattern can be produced by using semolina grains sprinkled on oil between + & - high voltage metal conductors The line of force or Field line direction is the path a small positive test charge would follow if free to move + Electric field patterns 90o An electric field pattern can be produced by using semolina grains sprinkled on oil between + & - high voltage metal conductors + The line of force or Field line direction is the path a small positive test charge would follow if free to move + Electric field patterns 90o An electric field pattern can be produced by using semolina grains sprinkled on oil between + & - high voltage metal conductors + + The line of force or Field line direction is the path a small positive test charge would follow if free to move Two types of charge - - - + + + Same charges repel, different charges attract Same charges repel, different charges attract How rubbing can produce static electricity At the start each material has no overall charge. Friction rubs electrons off the cloth onto the surface atoms of polythene. The polythene gains electrons and becomes negatively charged. However, acetate becomes positively charged Insulators do not have any delocalised electrons, They are all firmly attached to individual atoms What force keeps the electrons inside the atom? Region of excess Delocalised electrons ‘positive charges’ Region of excess Delocalised electrons ‘positive charges’ Electrons in the metal object are repelled by the negatively charged rod Because ‘like charges repel” Region of excess Delocalised electrons ‘positive charges’ Electrons in the metal object are repelled by the negatively charged rod Because ‘like charges repel” If the rod touches the conductor electrons flow off the rod and onto the conductor leaving both objects negatively charged ELECTRICAL DISCHARGE - + A charged conductor can be discharged by connecting it to earth. Electrical potential energy or potential difference between the conductor and the ground If the voltage is high enough the air molecules will ionise and a spark discharge occurs. - Ionisation is the ability to remove electrons from atoms leaving a trail of positive ions. ( thick copper strip ) slowly and safely An experiment to show that current is a moving charge Carbon coated ball on nylon thread Van der Graff generator micro ammeter An experiment to show that current is a moving charge Carbon coated ball on nylon thread _ _ + _ + _ The negative charges on the metal plate attract the ball An experiment to show that current is a moving charge Carbon coated ball on nylon thread _ _ + _ + _ The negative charges on the metal plate attract the ball _ _ _ _ The ball receives negative charge and is repelled away carrying the charges across to the other plate An experiment to show that current is a moving charge For AS PHYSICS we said: The faster the charges are carried across from one plate to the other the greater the current flows: Charge = Current X Time Q = I X T Coulombs Amps seconds Charge = Current Q = I Coulombs Amps X X Time T seconds Example: Calculate the amount of charge flowing passed a point in a wire carrying a current of 5 Amps in 10 minutes. Charge = Current Q = I Coulombs X Time X T Amps seconds Example: Calculate the amount of charge flowing passed a point in a wire carrying a current of 5 Amps in 10 minutes. Q = I Q Q = = 5 3000 X T x 10 x 60 Coulombs of charge The faster the charges are carried across from one plate to the other the greater the current flows: Current flowing depends on : * Charge on the ball * Frequency of transfer So: I=Qf = Charge Q Time of one cycle The faster the charges are carried across from one plate to the other the greater the current flows: Current flowing depends on : * Charge on the ball * Frequency of transfer So: Q U E S T I O N I=Qf = Charge Q Time of one cycle The faster the charges are carried across from one plate to the other the greater the current flows: Current flowing depends on : * Charge on the ball * Frequency of transfer So: Q U E S T I O N I=Qf = Charge Q Time of one cycle The faster the charges are carried across from one plate to the other the greater the current flows: Current flowing depends on : * Charge on the ball * Frequency of transfer So: Q U E S T I O N I=Qf = Charge Q Time of one cycle The faster the charges are carried across from one plate to the other the greater the current flows: Current flowing depends on : * Charge on the ball * Frequency of transfer So: Q U E S T I O N I=Qf = Charge Q Time of one cycle The faster the charges are carried across from one plate to the other the greater the current flows: Current flowing depends on : * Charge on the ball * Frequency of transfer So: Q U E S T I O N I=Qf = Charge Q Time of one cycle Chips and Charge Tiny circuits get damaged Electrons are attracted onto the chips pins via ‘earthed’ fingers If the ‘earth’ is removed the chips remain (oppositely )charged – by induction ! + Electric field patterns 90o The electric field pattern can be produced by using semolina grains sprinkled on oil between + & - high voltage metal conductors + + The line of force or Field line direction is the path a small positive test charge would follow if free to move