Transformer ~can either “step up” or “step down” the voltage provided to it. ~can either “step up” or “step down” the voltage provided to it. i.e. with the appropriate transformers you could make a 12 V current 24 V or 6 v. i.e. with the appropriate transformers you could make a 12 V current 24 V or 6 v. Or 120 V can be 6 V Or 120 V can be 6 V It is created by wrapping two different wires around the same conductor It is created by wrapping two different wires around the same conductor

Transformer Power source output input Primary Secondary

How a transformer works The change is caused by the number of loops (turns) on the primary and secondary. The change is caused by the number of loops (turns) on the primary and secondary. Assume both have 1 turn (loop), and the primary is a 12 V source Assume both have 1 turn (loop), and the primary is a 12 V source then the primary would induce a magnetic field in the conductor, which will induce an electric current in the secondary with 12 V then the primary would induce a magnetic field in the conductor, which will induce an electric current in the secondary with 12 V

Now transforming If the primary 1 V has one turn and the secondary has two turns, then each loop will get a 1 V, so it will have a total to 2 V. If the primary 1 V has one turn and the secondary has two turns, then each loop will get a 1 V, so it will have a total to 2 V. If the primary 2 V has two turns and the secondary has one turn, the secondary will have 1 V. If the primary 2 V has two turns and the secondary has one turn, the secondary will have 1 V. One of the major reasons AC is used as the primary power source is the ease is stepping up or stepping down the voltage as needed One of the major reasons AC is used as the primary power source is the ease is stepping up or stepping down the voltage as needed

Equation Primary voltage= Secondary voltage # of primary turns # of secondary turns Primary voltage= Secondary voltage # of primary turns # of secondary turns The power in must equal the power out (law of conservation of energy) The power in must equal the power out (law of conservation of energy) P = I VP in = P out P = I VP in = P out Stepping up the voltage decreases the current and vice versa. Stepping up the voltage decreases the current and vice versa.

Question If the power in the lines is V with 200 turns going into a transformer with 50 turns what will the voltage be? If the power in the lines is V with 200 turns going into a transformer with 50 turns what will the voltage be? V V

Power line transmission To transfer electricity across long distances you have to use extremely high voltage (like 120,000 V) and low current To transfer electricity across long distances you have to use extremely high voltage (like 120,000 V) and low current Otherwise you lose a lot of energy due to heating of the wire Otherwise you lose a lot of energy due to heating of the wire This is easily stepped down to 120 V used in our houses. This is easily stepped down to 120 V used in our houses. It also steps up the current we need. It also steps up the current we need.

Electromagnetic Radiation electromagnetic induction occurs without a wire for the current to travel through. electromagnetic induction occurs without a wire for the current to travel through. Moving any charged object (like a balloon rubbed on your head) will create… Moving any charged object (like a balloon rubbed on your head) will create… A moving magnetic field which in turn will create… A moving magnetic field which in turn will create… A moving electric field which causes… A moving electric field which causes… This continuously repeats This continuously repeats

EM wave

How fast do these waves go Since the waves travel due to a constant electromagnetic induction they always travel at the same speed. Since the waves travel due to a constant electromagnetic induction they always travel at the same speed. This speed is exceptionally fast, as a matter of fact it is the fastest anything can ever go This speed is exceptionally fast, as a matter of fact it is the fastest anything can ever go This speed is…. This speed is…. 3.0 x 10 8 m/s in a vacuum. 3.0 x 10 8 m/s in a vacuum.

homework Pg 758 Pg ; ; 19-22