4th Grade Lesson

design and build simple circuits

Background - Students should design and build simple series and parallel ciircuits with wires batteries and bulbs.

A simple series circuit consists of two or three light bulbs wired together with a battery in a single loop. If the filament of one bulb breaks (or one bulb is removed from its socket), the single-circuit loop is broken and all the lights go out.

Make a parallel circuit by extending two wires, parallel to each other, from the poles of a battery. Then they connect two or three bulbs, individually, across the parallel wires. If one of the bulb filaments is broken, the other bulbs still remain lit.

Vocabulary

Click the link for the Harcourt Science Glossary  
circuit A path that is made for an electric current
electric current A flow of electric charges

electric cell

 A battery that supplies energy to move charges through a circuit
conductor A material that electric current can pass through easily
insulator A material that current cannot pass through easily
resistor A material that resists the flow of current but doesn't stop it
series circuit A circuit that has only one path for current
parallel circuit A circuit that has more than one path along which current can travel

Lesson

To make a light bulb work, there has to be a flow of electrons in a circuit, or a circle, so that the receiver (light bulb) can have a constant supply of electricity. To create a circuit, use a battery, light bulbs and wires. You have to wire them just right to make the bulb light. Go to the activity to do this

Below are examples of how to wire two or more bulbs in a circuit.

Series Circuit

In series circuits one wire loop connects all the components, so current flows sequentially through the components in the One loop-

 
  Two bulbs in series will be dimmer than one bulb on its own. This is because it is harder for the electrons to pass through two bulbs than one.

If one bulb was to blow, then the circuit would be broken and the other one would go out as well.


Parallel Circuit In parallel circuits several loops of wires connect the components.
 

Two bulbs in parallel will still glow brightly. This is because each one is getting the full battery voltage.

However, two bright bulbs will take more current than a single bright bulb so the battery will not last as long.

If one bulb blows, there is still a complete circuit through the other bulb so it keeps glowing brightly.

 

Current

Current is measured in amperes (A). It is a measure of how many electrons are moving around the circuit. The higher the current, the greater the flow of electrons. Current is measured using an ammeter.

There must be a complete circuit for the electrons to flow. If the circuit is broken, the flow of electrons will stop.

Voltage

Batteries have a voltage marked on the side. it is measured in volts (V). It shows how much "push" the battery is giving the electrons to get them round the circuit. The higher the voltage the more energy each electron is given.

The more energy an electron has, the brighter it will make a bulb when they flow through it. Voltage is measured using a voltmeter

Activity - Lighting a bulb

Review - Review this lesson here