Electric Circuits

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Electric Current – the movement or flow of electric charges from one place to another.

Electric Circuit – a controlled path in which electric current passes through. Electric circuits are used to convert electrical energy into other forms of energy that we need such as heat or light.

Examples of How Circuits do this:

Flashlight - light energyElectric Kettle - thermal/heat energyCan opener – mechanical energyBuzzer\Bell – sound energy

The Parts of an Electric Circuit

Circuits, whether they are a study lamp, flashlight, or an experimental circuit all operate in essentially the same way, using 4 basic parts:

Parts of an Electric Circuit

• All electric circuits have the same four basic parts:

– Source of electrical energy

– Electric load

– Electric circuit control device

– Connectors

A Typical Circuit

Energy Source

Circuit Control Device

Electrical Load

Connectors

Source of Electrical Energy

• All circuits require a power source.

• The power source can be:

– a battery

– a power outlet in your home or school

– a car battery

– a generator

– a photoelectric cell

Electrical Load

• The electrical load is actually the reason the electric circuit exists.

• It is the thing that requires the electrical energy.• More familiar electrical loads include:

– light bulbs– televisions– computers– toasters– dvd players

Electric Circuit Control Devices

• As the name suggests, this is a device for controlling an electric circuit.

• You know these devices as switches.

• They can be simple like a light switch or the switch on a computer.

• Other switches can be more sophisticated like the timer on a vcr or a microwave oven.

Connectors

• Connectors are the conductors that allow the electric current to flow from point A to point B.

• The most common connectors are wires, which come in all different shapes and sizes.

• The purpose of connectors is to provide a “controlled path” for the electric current to flow.

3. Electric Circuit Control Device – a switch that controls the electricity (turn on and off).

4. Connectors – the conducting wires that provide the controlled path for electric current to flow to each part of the circuit.

1. Source of electrical Energy – the place or thing that generates the electrical energy.2. Electrical Load – anything that converts electrical energy into the form of energy needed.

3

1

2

4

Closed Circuit – a circuit that is closed or “on” or allowing electricity to flow through.

Open Circuit – a circuit that is open or “off” or not allowing electricity to flow through.

Electric current flows in a continuous loop from the negative terminal of the cell, through the wires, the switch, and the electric load (light), and returns to the cell’s positive terminal.

Electric Circuit Diagrams and Symbols

Symbols are used to simplify the drawing of electric circuits.

Questions

• Page 301, 1-5, 7

Answers:

Q. 1. The difference between: Static electricity is electric charge that remains in a fixed position. Current electricity is electric charge that is moving in one or more paths. (the moving current of electricity is called an electric current – controlled or uncontrolled path.)

• Q3. The electric charge flows from the negative terminal of the dry cell – the switch-the bulb –positive terminal on the dry cell.

• This follows the law of electric charges (negative attracted to plus)

Question 4 – Part 1

Four electrical loads that convert electrical energy to light energy are:

• Light bulb In refrigerator• Ceiling light bulb• Microwave oven light• Warning light on stove

Question 4 – Part 2

Four electrical loads that convert electrical energy to mechanical energy are:

Coffee grinderBlenderBread makerCan opener

Question 5

a) Wall switch for ceiling, on/off for toaster, stove knobs

b) Ceiling light, dryer timer control, washing machine switch

c) Switch for headlights, push button for horn, switch for defrost