Electrical Circuit StudentBooklet En

Electrical circuitStudent booklet

Electrical circuit - INDEX - 2006-04-06 - 16:43

- INDEX -

Electrical circuit

In this module, we will explain what an electric circuit is and what parallel/series circuits are. We will begin with talking about what basic components you can find in them. We will also do some practical exercises that will help you understand the difference between the two types of circuits.

Series circuit Parallel circuit Components Parallel circuit with two switches Lab: Current in a series circuit Lab: Current in a parallel circuit Lab: Rear lamp unit Sum up Assessment

Contents

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Electrical circuit - BasEl_circuit_02.swf - 2006-04-06 - 16:43

An electrical circuit leads a current from a voltage source, through a number of components, and then back to the voltage source. There are two kinds of circuits, series circuit and parallel circuit. _

In a series circuit all the electrical loads are connected in series after each other so there is only one way for the current to flow.When you close the switch the current can flow through both bulbs, lighting them.

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In a parallel circuit all components are connected to one another in parallel. This means that the current can flow in several different paths instead of just one way. _

When you close the switch the current can flow through both bulbs, lighting them.

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Voltage source The voltage source supplies the circuit with voltage. Without the voltage source there would be no current through the circuit. Batteries and generators are examples of voltage sources. _

Electrical loadThe electrical load transforms current into heat, light or movement. Examples of electrical loads are heated rear windscreens (heat), bulbs (light) and motors (movement). _

Power cableThe power cable conducts current to the various components in the circuit. It is made from a good conductive material and has a protective sleeve. _

GroundThe ground conducts current from the electrical load to the voltage source. In trucks there are often several different components to the ground. The electrical load may be connected to the truck frame by a cable. In turn the truck frame is connected to the voltage source by a different cable. This completes the circuit. _

SwitchThe switch makes it possible to close and open the circuit. _

FuseIf, for some reason, current increases to a level greater than that for which the circuit is rated, cables and components may overheat and be damaged. In the worst case overheating could cause a fire. The fuse prevents this by opening the circuit first.

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We will now extend the parallel circuit by adding another switch. _

When you close switch 1 the current can flow through bulb 1, lighting it. _

When you close switch 2 the current can flow through bulb 2, lighting it. _

When you close both switches the current can flow through both bulbs and light them.

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Electrical circuit - BasEl_circuit_excer_05.swf - 2006-04-06 - 16:43

Lab: Current in a series circuitConnect the bulbs somewhere on the lab bench. Use the components to create a closed circuit so that current can flow from the positive terminal of the power supply to its negative terminal via the bulbs.

1. Connect the components according to the picture.

2. Measure the current that runs through the light bulb: _______

3. Replace the jumpers with two more light bulbs so they are connected in series and notice how the current changes as every bulb is mounted on the lab bench. Note the Currents:Circuit with two bulbs: _______

Circuit with three bulbs: _______

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Electrical circuit - BasEl_circuit_excer_08.swf - 2006-04-06 - 16:43

Lab: Current in a parallel circuitConnect the bulbs somewhere on the lab bench. Use the components to create a closed circuit so that current can flow from the positive terminal of the power sypply to its negative terminal via the bulbs.

1. Connect the components according to the picture.

2. Measure the current that runs through the light bulb: _______

3. Mount two more light bulbs and notice how the current changes as every bulb is mounted on the lab bench. Note the Currents:Circuit with two bulbs: _______

Circuit with three bulbs: _______

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Electrical circuit - BasEl_circuit_excer_08b.swf - 2006-04-06 - 16:43

Lab: Rear lamp unitConnect the component according to the picture.Do the following measuring and note down the results:1) Voltage measurement, single lamp.

_____________________________________________________

2) Voltage measurement, all lamps.

_____________________________________________________

3) Voltage measurement, acoustic reverse warning.

_____________________________________________________

4) Current measurement, single lamp.

_____________________________________________________

5) Current measurement, all lamps.

_____________________________________________________

Question: Let say we had an unwanted resistance in any of these circuits, what would be the consequence?_____________________________________________________

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Electrical circuit - BasEl_circuit_sumup_09.swf - 2006-04-06 - 16:43

Sum upLab: Current in a series circuitIn a series circuit, all the electrical loads are connected in series after each other so there is only one way for the current to flow. Several electrical loads share the available voltage. That's why the current will decrease as you add on more loads, like the light bulbs in this example.

The reason why the circuit not seem to follow Ohm's law is that the bulbs temperature affects its resistance. If the bulbs are replaced against the ordinary resistors that we use in our elaborations, you will see that the use of current will follow Ohm's law in a more predictable way.

Lab: Current in a parallel circuitIn a parallel circuit the current can flow several different ways. We could say that the circuit has different branches. The current in each branch depends on how great the resistance is. The current is greatest in the branch with the lowest resistance. The total current in the circuit is equal to the sum of all currents flowing through the different branches. The voltage available in each branch is the same as the supply voltage, in this case 12V.

Lab: Rear lamp unitThis is a good example where we have different circuits in a truck component. If we learn how to measure both voltage and current on a loose component like this, we can use this knowledge in a real fault-tracing situation. This is the objective with this exercise.

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Electrical circuit - BasEl_circuit_assess_10.swf - 2006-04-06 - 16:43

Assessments questions1. Which component drives the current through an electrical circuit?

2. Which component usually acts as ground in a truck?

3. Why does an electrical circuit need a fuse?

4. What component makes it possible to close and open a circuit?

5. Which components is an electrical load?

6. What are the circuits called where the current only has one way to go?

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Electrical Circuit StudentBooklet En