Current Current There are two kinds of current: There are two kinds of current:

CurrentCurrent

CurrentCurrent

• There are two kinds of current:There are two kinds of current:

CurrentCurrent

• There are two kinds of current:There are two kinds of current:1.1. Direct currentDirect current

CurrentCurrent

• There are two kinds of current:There are two kinds of current:1.1. Direct currentDirect current2.2. Alternating currentAlternating current

Direct currentDirect current

Direct currentDirect current

• DC flows in DC flows in one directionone direction• DC is the kind of current that comes from DC is the kind of current that comes from

batteries.batteries.

Alternating currentAlternating current

Alternating currentAlternating 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 do we use AC instead of DC?Why do we use AC instead of DC?

Why do we use AC instead of DC?Why do we use AC instead of DC?

Why do we use AC instead of DC?Why do we use AC instead of DC?

Why do we use AC instead of DC?Why do we use AC instead of DC?

Why do we use AC instead of DC?Why do we use AC instead of DC?

Why we use AC instead of DCWhy we use AC instead of DC

• AC can be more easily transmitted over long AC can be more easily transmitted over long distances than DC.distances than DC.

Why we use AC instead of DCWhy we use AC instead of DC

• AC can be more easily transmitted over long AC can be more easily transmitted over long distances than DC.distances than DC.

• Why?Why?

Why we use AC instead of DCWhy we use AC instead of DC

• AC can be more easily transmitted over long AC can be more easily transmitted over long distances than DC.distances than DC.

• Why?Why?• Because of Because of transformerstransformers

TransformersTransformers

Step-up transformersStep-up transformers

• Turns lower voltages into higher onesTurns lower voltages into higher ones• Fewer turns on the primary side than the Fewer turns on the primary side than the

secondary one.secondary one.

Step-up transformersStep-up transformers

Step-down transformersStep-down transformers

• Turns higher voltages into lower ones.Turns higher voltages into lower ones.• More turns on the primary side than the More turns on the primary side than the

secondary one.secondary one.

Step-down transformersStep-down transformers

Step-down transformersStep-down transformers

Electromagnetic InductionElectromagnetic Induction

Electromagnetic InductionElectromagnetic Induction

• E.i. describes the production of E.i. describes the production of electricity by using a magnetic field.electricity by using a magnetic field.

• This is how generators “make” This is how generators “make” electricity.electricity.

• Generators Generators convert mechanical energy convert mechanical energy into electrical energyinto electrical energy. .

Electromagnetic InductionElectromagnetic Induction

Electromagnetic InductionElectromagnetic Induction

POWERPOWER

POWERPOWER

• Power is the Power is the raterate at which devices use energy. at which devices use energy.

POWERPOWER

• Power is the Power is the raterate at which devices use energy. at which devices use energy.• The unit of power measurement is the The unit of power measurement is the watt watt

(W)(W). It measures how many units of energy . It measures how many units of energy are used per second. are used per second.

POWERPOWER

• Power is the Power is the raterate at which devices use energy. at which devices use energy.• The unit of power measurement is the The unit of power measurement is the watt watt

(W). (W). It measures how many units of energy It measures how many units of energy are used per second. are used per second.

• Energy is measured in joules (J)Energy is measured in joules (J)

POWERPOWER

• The power rating of a device is directly The power rating of a device is directly proportional to the current flowing through proportional to the current flowing through the device and the voltage in the circuit.the device and the voltage in the circuit.

POWERPOWER

• The power rating of a device is directly The power rating of a device is directly proportional to the current flowing through proportional to the current flowing through the device and the voltage in the circuit.the device and the voltage in the circuit.

• In other words...In other words...

POWERPOWER

• The power rating of a device is directly The power rating of a device is directly proportional to the current flowing through proportional to the current flowing through the device and the voltage in the circuit.the device and the voltage in the circuit.

• In other words...In other words...The Power FormulaThe Power Formula

Power = current x voltagePower = current x voltage P = I x VP = I x V

Math Time!!

Now, stop writing (and complaining) and watch this.