1

Applied Single Award & Entry LevelWJEC ‘Entry Level’ taught in conjunction with content from

Applied Single Award Science – to allow access to WJEC Double Award Science GCSE.

Applied Context: A large number of electrical devices are now used in our homes, at work, or for leisure. In this topic learners will explore simple electric circuits and understand how the construction of a circuit affects the current and voltage across components. They will also be introduced to key concepts and relationships that need to be considered when building a circuit. Learners can apply their knowledge in a number of fields including electrical engineering, electronics and communications.

Please note:

Some of the tasks and questions that you are expected to complete will not be in this booklet.

You will need to bring the following to each of your lessons:

exercise book pen, pencil, ruler, rubber and calculator.

1.1.4 ‘Building Electrical Circuits’

Name: _______________________________________Class: ________________________________________ Teacher: _____________________________________

Subject Specific Targets Single Applied 1.1.4

BEFORE Unit

I have LEARNE

D

I am able to draw & recognise the symbols of components (cell, switch, lamp, voltmeter, ammeter, resistor, variable resistor, fuse, LED, thermistor, LDR, diode) used in electrical circuits, a.c. power supply, d.c. power supply and variable d.c. power supply.I know that series circuits in which the current is the same throughout a circuit and voltages add up to the supply voltage; parallel circuits in which the voltage is the same across each branch and the sum of the currents in each branch is equal to the current in the supply. Including appreciation of types of household circuits e.g. ring main, household lighting circuits.I understand adding components in series or parallel to change the total resistance of a circuit; physical factors that affect the resistance of thermistors and LDRs.I know voltmeters and ammeters to measure the voltage across and current through electrical components in electrical circuits. I know that an ammeter must be connected in series and a voltmeter must be connected in parallel.I can use circuits to investigate how current changes with voltage for a component e.g. for a resistor (or wire) at constant temperature, a filament lamp and a diode. The circuits would include a variable resistor. Including knowledge of how: • R varies with V for a lamp • R varies with positive and negative voltages for a diode and that normally a diode will not conduct until a particular voltage is reached. Current plotted on the y-axis and voltage on the x-axis.I understand the significance of, and the relationship between current, voltage and resistance. The qualitative and quantitative relationships should be known

I know how adding components in series increases total resistance in a circuit; how adding components in parallel decreases total resistance in a circuit. I know how to calculate total resistance and current in a series circuit; how to select an appropriate fuse for a circuit; how to calculate the total resistance and total current in a parallel circuit.

I can use mathematical equations to find useful information:

On foundation tier the equation will be given in the form required.

SPECIFIED PRACTICAL WORK• Investigation of the current-voltage (I-V) characteristics for a component

2

Target Sheet: (dual) Applied Single Award & Entry Level WJEC

Single Award = 1.1.4 “Building electric circuits”Entry Level = 1.1.3 “Building electric circuits”

Subject Specific Targets Entry Level 1.1.3 BEFORE Unit

I have LEARNE

DI can recognise and draw symbols of components (e.g. cell, switch, lamp, voltmeter, ammeter, resistor, diode, lamp, fuse) used in electrical circuits. I understand series circuits in which the current is the same throughout a circuit and voltages add up to the supply voltage.I understand parallel circuits in which the voltage is the same across each branch and the current in each branch is equal to the current in the supply.I have an appreciation of types of household circuits e.g. ring main, household lighting circuits.I can recognise the energy changes that take place in a circuit.I know that an ammeter must be connected in series and a voltmeter must be connected in parallel.I know that voltmeters and ammeters to measure the voltage across and current through electrical components in electrical circuits.

SYMBOLSIt is important to know the symbols of components in electrical circuits.Tasks:

3

My personal target is to: -

I will achieve this by: -

1. Copy these neatly into your exercise book. You will need to learn their names and be able to draw each of them!

The thin wire in the centre of the fuse has high resistance and will over heat if there is a ‘surge’ in current. This will make the fuse overheat and melt. It will then ‘switch off’ the circuit so that nobody gets electrocuted.

4

Activity: A fuse ‘is a deliberate weak spot in a circuit’. Your teacher will demonstrate a fuse in action. Explain how the fuse works.

ACTIVITYMake the following circuit diagrams, draw them into your exercise book and identify the components.

1.

2.

3.

5

Task: Make some alternating current using a magnet, coil, movement and a centre spot meter.

Alternating Current (a.c.) is made in a power station. It is easier to generate than d.c.

Direct Current (d.c.) This is current that flows continually in either a positive or negative direction. It is the current produced by a cell or a battery.

AMMETERS

VOLTMETERS

How are ammeters and voltmeters connected in a circuit?

Activity: Connect up the following circuit. Measure the current and voltage.

There are two types of electrical circuit: series circuits and parallel circuits. In a series circuit all of the components follow the same path. In a parallel circuit there are branches where the components sit. SERIES CIRCUIT

6

This is the symbol for an ammeter:

Ammeters are always connected in series.

This is the symbol for a voltmeter:

Voltmeters are always connected in parallel.

Voltmeters measure the driving force around the circuit. This is called ‘potential difference’. The unit of potential difference is the ‘Volt’ (V)

Ammeters measure current. The unit of current is the ‘Amp’ (A).

Ammeters are connected in

series

Voltmeters are connected in

parallel

All of the components follow the same path. Also, the current is the same throughout the circuit and the voltage across each component adds up to the voltage of the power supply.Task: Calculate the current in the circuit diagrams below:

PARALLEL CIRCUIT

7

Task: Set up the parallel circuit similar to on the left. How bright are the bulbs compared to a series circuit?Remove a bulb. What happens?Measure the current and voltage at different points in the circuit.

Task: Set up the series circuit on the right. How bright are the bulbs? Add another bulb – what happens to the brightness?Remove a bulb. What happens?Measure the current and voltage at different points in the circuit.

In a parallel circuit the components are in branches. Here the voltage across all components is the same and the current within each branch is equal to the current of the power supply.

ADVANTAGES, DISADVANTAGES AND EXAMPLESTask: Copy and complete table in your exercise books

Circuit Advantages Disadvantages Examples8

Task: Set up the parallel circuit similar to on the left. How bright are the bulbs compared to a series circuit?Remove a bulb. What happens?Measure the current and voltage at different points in the circuit.

typeSeries

Parallel

Summary of Series and Parallel Circuits

9

10

11

Specified Practical Activity:

Complete the risk assessment in your exercise books.Hazard Risk Control Measure

Hot lamps can burn Burning skin on hot lamps Allow them to cool befoe touching them

Wire could get hotThin wireElectricty

Resistance:12

We get resistance when an electric current flows when charged particles called electrons move through a conductor. The moving electrons can collide with the atoms of the conductor. This makes it more difficult for the current to flow, and causes resistance. Electrons collide with atoms more often in a long wire than they do in a short wire. A thin wire has fewer electrons to carry the current than a thick wire. This means that the resistance in a wire increases as:

the length of the wire increases the thickness of the wire decreases

To calculate resistance, we use the following equation:

Task: Calculate the resistance in a circuit if the voltage is 12V and the current is 3A.To gain full marks, write out the equation, show your workings, calculate your answer and use the correct unit.

Current Voltage graphsYou need to be able to recognise the shapes of the graphs:

13

Resistance = Voltage (V)

(Ohms) Current (A)

The Filament lamp:The filament lamp does not follow Ohm's Law. The resistance of a filament lamp increases as the temperature of its filament increases. As a result, the current flowing through a filament lamp is not directly proportional to the voltage across it. This is the graph of current against voltage for a filament lamp.

A resistor at constant temperature:The current flowing through a resistor at a constant temperature is directly proportional to the voltage across the resistor. The graph shows what happens to the current and voltage when a resistor follows Ohm's Law.

Test Yourself:

14

A diode:Current will only flow in one direction. There is very high resistance in the reverse direction.

15

16

17

18

Past paper questions:1.

2.

19

Plot the data and draw a suitable line (3)

3.

20

4.

21

5.

6.

22

23

7.

PISA Style questions:

24

25