Electricity andcircuits

Electricity andcircuits

Electricity is the flow of electric charges, typically through wires, conductors, and electrical devices.

Sometimes we can see the effects of electricity in nature.

What is electricity?What is electricity?

What is electric current?What is electric current?

Current is measured in amperes (A), also called amps.

Electric current is the flow of charged particles, usually through wires and circuits.

Animated illustration, page 472

How do we measure electric current?How do we measure electric current?

Electric current is measured using an ammeter or, more commonly, a digital multimeter.

In order to properly measure current, all the current must flow into the meter and back out again, into the circuit being tested.

In this circuit, I = 0.3 amps.

What is an electric circuit?What is an electric circuit?

An electric circuit is a conducting path through which electric current can flow.

The symbol for electric current is I.

Charge is conservedCharge is conservedElectric current I must be the same at all points in a simple, single-loop circuit.

Charge can never be created or destroyed. All the charge that flows through one point in the circuit must flow through the next point also.

I

I

An open circuit does not have a complete path so no current flows.

A closed circuit has a complete path, allowing current to flow.

Open and closed circuitsOpen and closed circuits

Common circuit elementsCommon circuit elements

Knife blade switchesKnife blade switches

A knife blade switch uses a mechanical lever to open/close a circuit connection.

The handle is an insulator, so you won’t get a shock when you touch it!

When attaching a knife blade switch to a circuit, do so with it in the open position.

What is a short circuit?What is a short circuit?

Power and ground are connected from an external source to strips on the edge of the breadboard.

What is a breadboard?What is a breadboard?

A circuit breadboard is a device used for mounting and prototyping electric circuits.

In Investigation 17A you will build electric circuits using a circuit breadboard.

Exploring the ideasExploring the ideas

InvestigationInvestigationPart 1: Exploring the connections on a breadboard

1. Use the continuity setting on a multimeter to test whether the probes are connected to each other.

2. Identify 3 kinds of connections: power (red); ground (blue); and terminal (black).

3. Draw a diagram showing the connections between the holes in the breadboard.

InvestigationInvestigationQuestions

a. Where should you connect the positive and negative terminals of a battery?

b. Where should you connect other circuit components, such as lamps and resistors?

c. How are the holes in a circuit board connected to each other?

Draw a diagram showing the connections between the holes in the breadboard on your student assignment sheet.

InvestigationInvestigation

InvestigationInvestigationPart 2: Wiring a simple circuit

1. Connect power and ground from a +3 V voltage source (or 2 D-cells) to the breadboard.

1. Connect a simple circuit with one lamp.

One lead connects to the breadboard's power strip; the other to the ground strip.

InvestigationInvestigation

If not, check all your connections.

The two ends of the lamp must be in different rows.You can use ANY rows.

This example uses rows 9 and 10.

Does your lamp illuminate?

How can you use wires to create a switch?

Does your lamp go on and off as you connect/disconnect the switch?

Create a simple switchCreate a simple switch

Short circuitShort circuit

How can you use a wire to modify your circuit to create a short circuit?

Hint: use a wire to bypass the lamp!

Short circuitShort circuit

How can you use a wire to modify your circuit to create a short circuit?

What should happen to the lamp if you create the short circuit correctly?

AssessmentAssessment2. Label each of these electrical symbols with the name of the

electrical component it represents: battery; resistor; lamp; switch; or wire.

wire switch battery lamp resistor

AssessmentAssessment2. Label each of these electrical symbols with the name of the

electrical component it represents: battery; resistor; lamp; switch; or wire.

AssessmentAssessment4. Identify the following circuits:

AssessmentAssessment

Short circuit Open circuit Closed circuit

4. Identify the following circuits:

How to strip the plastic insulation off the ends of a wire

A small amount of plastic insulation must be removed from the ends of wires to use them in circuits.

If your wires are not “pre-stripped,” then you will need to use a wire stripper to remove a small amount of the insulation.

Going furtherGoing further