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22.3 Inductance. pp. 814 - 819 Mr. Richter. Agenda. Warm Up Notes: Mutual Inductance Transformers. Objectives: We Will Be Able To…. Describe how mutual induction occurs in circuits. Calculate the potential difference from a step-up or step-down transformer. Warm-Up:.
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22.3 Inductance pp. 814 - 819 Mr. Richter
Agenda • Warm Up • Notes: • Mutual Inductance • Transformers
Objectives: We Will Be Able To… • Describe how mutual induction occurs in circuits. • Calculate the potential difference from a step-up or step-down transformer.
Warm-Up: • Transformers are used to “step down” the voltage from power lines, about 100,000 V to the 120 V household levels. If the voltage decreases, what must increase as a result?
Mutual Inductance • If a coil with current running through it is wrapped around an iron core, a magnetic field is generated. • If a second coil is wrapped around the core, current is induced in the second coil. • This process transferring the current of one circuit to a nearby circuit is called mutual inductance.
Mutual Inductance • If the number of turns of the wire (N1) of the primary coil is different from the number of turn of the secondary coil (N2), the amount of current flowing in each circuit will change. • As a result, the voltage in the second circuit will be different than the voltage in the first.
Transformers • A transformer is a device that changes one potential difference to a different potential difference. • If the number of coils in the secondary coil is more than the primary, the voltage is increased. • This is called a “step-up” transformer. • A “step-down” transformer does the opposite. Voltage decreases.
Transformers • The voltage change in a transformer is directly proportional to the ratio of the number of turns of the wire in the coil. • If the voltage increases, the current flowing through the secondary coil decreases, and vice versa. • Power through both circuits stays the same.
Transformers • A step-up transformer is used on a 120 V line to proved a difference of 2400 V. If the primary coil has 75 turns, how many turns must the secondary coil have? • N2 = 1500 turns
Wrap-Up: Did we meet our objectives? • Describe how mutual induction occurs in circuits. • Calculate the potential difference from a step-up or step-down transformer.
Homework • p. 823 #29-31, 35, 36