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## Current

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**Current**• There are two kinds of current:**Current**• There are two kinds of current: • Direct current**Current**• There are two kinds of current: • Direct current • Alternating current**Direct current**• DC flows in one direction • DC is the kind of current that comes from batteries.**Alternating current**• AC flows back and forth rapidly. • In North America it flow back and forth 60 times a second. This is called 60 Hertz**Why we use AC instead of DC**• AC can be more easily transmitted over long distances than DC.**Why we use AC instead of DC**• AC can be more easily transmitted over long distances than DC. • Why?**Why we use AC instead of DC**• AC can be more easily transmitted over long distances than DC. • Why? • Because of transformers**Step-up transformers**• Turns lower voltages into higher ones • Fewer turns on the primary side than the secondary one.**Step-down transformers**• Turns higher voltages into lower ones. • More turns on the primary side than the secondary one.**Electromagnetic Induction**• E.i. describes the production of electricity by using a magnetic field. • This is how generators “make” electricity. • Generators convert mechanical energy into electrical energy.**POWER**• Power is the rate at which devices use energy.**POWER**• Power is the rate at which devices use energy. • The unit of power measurement is the watt (W). It measures how many units of energy are used per second.**POWER**• Power is the rate at which devices use energy. • The unit of power measurement is the watt (W). It measures how many units of energy are used per second. • Energy is measured in joules (J)**POWER**• The power rating of a device is directly proportional to the current flowing through the device and the voltage in the circuit.**POWER**• The power rating of a device is directly proportional to the current flowing through the device and the voltage in the circuit. • In other words...**POWER**• The power rating of a device is directly proportional to the current flowing through the device and the voltage in the circuit. • In other words... The Power Formula Power = current x voltage P = I x V**Now, stop writing (and complaining)**and watch this.