Electricity 3 Thomas Edison

Lesson Objectives To know the differences between series and parallel circuits To know where different circuits are used. To apply your knowledge to different scenarios

3V 1.5V What happens if the bulbs have different resistances? Keywords: To know the differences between series and parallel circuits To know where different circuits are used. To apply your knowledge to different scenarios

3V 22 In a SERIES circuit, the total RESISTANCE is the sum of all of the resistances added together, so = 5  Keywords: To know the differences between series and parallel circuits To know where different circuits are used. To apply your knowledge to different scenarios 33 So, what is the current through the 2  bulb? Remember, V = IR 6 = I x 2 6/2 = 3A

N Circuit 1* Circuit 2 Two different circuits – what is different? Keywords: To know the differences between series and parallel circuits To know where different circuits are used. To apply your knowledge to different scenarios

Circuit 3 N Circuit 1* Circuit 2 Circuit 4 Build the following circuits and record the brightness of the bulbs Keywords: To know the differences between series and parallel circuits To know where different circuits are used. To apply your knowledge to different scenarios

N Circuit 1* Circuit 3Circuit 2 Circuit 4 N N N N N N N N N Build the following circuits and record the brightness of the bulbs Keywords: To know the differences between series and parallel circuits To know where different circuits are used. To apply your knowledge to different scenarios Conclusion: In a parallel circuit, the potential difference across all components is the same.

A3A3 A2A2 A1A1 A 1, A 2 and A 3 are ammeters. Remember: In a parallel circuit, the total current in the branches is the same as the current in the rest of the circuit. Or.. A 1 = A 2 + A 3 Keywords: To know the differences between series and parallel circuits To know where different circuits are used. To apply your knowledge to different scenarios In a parallel circuit, the current splits between the branches.

Example 1. Ammeter A 2 reads 0.18 amps and ammeter A 3 reads 0.24 amps. What does ammeter A 1 read ? A 1 = 0.42 amps A 1 = A 1 = A 2 + A 3 A3A3 A2A2 A1A1 Keywords: To know the differences between series and parallel circuits To know where different circuits are used. To apply your knowledge to different scenarios

Example 2. Ammeter A 1 reads 0.36 amps and ammeter A 3 reads 0.22 amps. What does ammeter A 2 read ? A 1 = A 2 + A 3 A 2 = 0.14 amps A 2 = 0.36 ▬ = A A3A3 A2A2 A1A1 Keywords: To know the differences between series and parallel circuits To know where different circuits are used. To apply your knowledge to different scenarios

Conclusion: Current is the shared between the branches of a parallel circuit. Potential Difference is equal across the components in a parallel circuit. Resistance depends on the current flowing through the component (as PD is the same). The bigger the resistance, the smaller the current. Keywords: I know some circuit symbols for common components. I know what is meant by resistance I know what is Ohm’s law.

What happens if we change the resistance of each bulb? Calculate the current through each bulb. (V = IR) Keywords: I know some circuit symbols for common components. I know what is meant by resistance I know what is Ohm’s law. 6V 11 22 33 I = V/R = 6/1 = 6A I = V/R = 6/2 = 3A I = V/R = 6/3 = 2A Total I = = 11A

Page 182/3 Answer Exam Style Questions Keywords: I know some circuit symbols for common components. I know what is meant by resistance I know what is Ohm’s law.

Flow of current. In a torch the current flows around in one direction – we call this d.c. (direct current). Electricity in the home uses a.c. (alternating current) which changes direction repeatedly. The frequency of an a.c. supply is the number of cycles it passes through per second. In the UK is 50Hz (50 times per second). Keywords: I know some circuit symbols for common components. I know what is meant by resistance I know what is Ohm’s law.

Potential Difference Keywords: I know some circuit symbols for common components. I know what is meant by resistance I know what is Ohm’s law.

Plugs Need a live wire (its PD changes every second) Need a neutral wire (connected to an Earth at the local sub station). Some items also have an additional Earth (metallic items in particular). The case is made of an insulator. Keywords: I know some circuit symbols for common components. I know what is meant by resistance I know what is Ohm’s law.

Plugs Which pin is longer and why? The Earth is longest – so the appliance is Earthed first. What alloy is used to make the contacts inside the plug? Brass (it is harder than copper) Keywords: I know some circuit symbols for common components. I know what is meant by resistance I know what is Ohm’s law.

Wire a plug Green & Yellow – Earth Blue (or black) – Neutral Brown (or red) - Live Keywords: I know some circuit symbols for common components. I know what is meant by resistance I know what is Ohm’s law.

Fuses Lengths of wire, which when get to hot melt and break the circuit. A fuse provides NO protection against electrocution more than 20mA which can be lethal and so items must be EARTHED. Keywords: I know some circuit symbols for common components. I know what is meant by resistance I know what is Ohm’s law.

Keywords: I know some circuit symbols for common components. I know what is meant by resistance I know what is Ohm’s law. Circuit breaker. It is an electromagnetic switch that open (cuts off) when the current is too high. It can be reset once the fault has been corrected. They are faster than fuses. They can be reset quicker.

Are you now able to…. I still feel unsure. I need some more help to understand. I feel ok. I need to do some more work to check my understanding. I am happy and feel I understand and can explain the main points. To know the differences between series and parallel circuits To know where different circuits are used. To apply your knowledge to different scenarios