1. Electrical Circuits

2. Energy transfer in circuits Energy cannot be created or destroyed. In all devices and machines, including electric circuits, energy is transferred from one type to another. When this circuit is connected, chemical energy stored in the battery is transferred via electrical energy to heat and light energy in the bulbs. The total amount of heat and light energy is the same as the amount of chemical energy lost from the battery.

3. Most of the energy from the battery does not produce light – most of it is wasted as heat! chemical energy from battery (e.g. 100J) heat energy of bulb 95 J transferred to 5 J transferred to bulb as light energy Energy transfer in electrical circuits

4. Batteries can power many electrical devices. What sort of energy is electrical energy transferred into in these electrical devices? What is the energy transfer?

5. boilerandpump radiator highpressurelowpressure flow of water An electrical circuit is like a central heating system in a house. There is a pump that pushes water around the system. There is a pump that pushes water around the system. radiator What is an electrical circuit? The water everywhere starts to move at the same time. The water everywhere starts to move at the same time. There are pipes that carry the water. There are pipes that carry the water. In the pipes the water is flowing. In the pipes the water is flowing.

6. What is an electrical circuit? Instead of a flow of water, electricity flows in an electrical circuit. The electrical current is pushed by the cell (or battery), which has the same function as the pump and boiler. The strength of push provided by the battery is called itsvoltage The electrical current is pushed by the cell (or battery), which has the same function as the pump and boiler. The strength of push provided by the battery is called its voltage. Thebulbin the circuit is like a radiator. An electrical device uses electrical energy supplied by the circuit. The bulb in the circuit is like a radiator. An electrical device uses electrical energy supplied by the circuit. The wires are like pipes; they carry the flow of electricity (calledcurrent) around the circuit. The wires are like pipes; they carry the flow of electricity (called current) around the circuit.

7. Drawing Circuits 1) A battery, a bulb and a switch ‘in series’ 2) A battery of cells, a switch and two bulbs in series

8. Components in an electrical circuit

9. The unit of measure for current is the amp, which has the symbol A. A Measuring current AA Current is measured using a device called an ammeter. In a circuit diagram, an ammeter is shown by the symbol In a circuit diagram, an ammeter is shown by the symbol. When measuring the current through a component, the ammeter is always connected in series (in the same loop) with that component.

10. Current in a series circuit If the current here is 2 amps… The current here will be… And the current here will be… In other words, the current in a series circuit is THE SAME at any point

11. Changing the current If a battery is added the current will ________ because there is a greater _____ on the electrons. If a bulb is added the current will _______ because there is greater ________ in the circuit

12. This is a simpleseriescircuit. This is a simple series circuit. What is a series circuit? In a simple series circuit, everything is connected in one loopacross the terminals of the battery. So there are not any points where the current can split or join (these are called junctions). In a simple series circuit, everything is connected in one loop across the terminals of the battery. So there are not any points where the current can split or join (these are called junctions). This circuit has two lamps connected in series. Circuits are always drawn using straight lines.

13. Here are some other simple series circuits: 2.A rheostat (or variable resistor) and a bulb connected in series: R1 R2 Examples of series circuits 1.Two resistances (resistors) connected in series: 1. Two resistances (resistors) connected in series:

14. 1. In a series circuit the current is the same in all parts of the circuit. Series circuits – key ideas 2. The supply voltage is shared between the components in a series circuit. (The sum of the voltage across each component is the same as the total supply voltage.) 3. The current depends on the voltage in any circuit.

15. Current in a parallel circuit A parallel circuit is one where the current has a ‘choice of routes’. Here comes the current… And the rest will go down here… Half of the current will go down here (assuming the bulbs are the same)…

16. Current in a parallel circuit If the current here is 6 amps The current here will be… And the current here will be…

17. Advantages of parallel circuits… There are two main reasons why parallel circuits are usedmore commonly than series circuits: There are two main reasons why parallel circuits are used more commonly than series circuits: 1)Extra appliances (like bulbs) can be added without affecting the output of the others. 2)If one appliance breaks it won’t affect the others either.

18. Comparing series & parallel circuits Series circuit Parallel circuit If one bulb blows they all go out. If one bulb blows only that one goes out. One switch operates all of the bulbs. Each bulb can be turned on and off with its own switch. The voltage across the power supply is shared between all of the bulbs. The voltage across each bulb is the same as across the power supply. The current from the power supply is low. The current from the power supply is high.

19. When measuring the voltage across a component, the voltmeter is always connected in parallel with (or across) the component. Voltage is measured using a device called a voltmeter. In a circuit diagram, a voltmeter is given the symbol. In a circuit diagram, a voltmeter is given the symbol. V This is still a series circuit. Measuring voltage V3V3V3V3 V2V2V2V2 V1V1V1V1 The voltage supplied by the battery is shared between all the components in a series circuit.

20. A V component here Voltage is measured by connecting the voltmeter across (or in parallel with) the component. V Measuring voltage across a resistance or a bulb R Components Voltage is measured in volts and the symbol for this is V.

21. Wiring a plug Earth wire Neutral wire Insulation Live wire Fuse Cable grip

22. Fuses Fuses are _______ devices. If there is a fault in an appliance which causes the ____ and neutral (or earth) wire to cross then a ______ current will flow through the _____ and cause it to _____. This will break the _______ and protect the appliance and user from further _____. Words – large, harm, safety, melt, live, circuit, fuse

23. Earth wires Earth wires are always used if an appliance has a _____ case. If there is a _____ in the appliance, causing the live wire to ______ the case, the current ‘_______’ down the earth wire and the ______ blows. Words – fuse, fault, metal, surges, touch

24. Circuit breakers If the current becomes too high the __________ is activated. This will ______ the iron and the contact will be _______. This will break the circuit. Circuit breakers have two main advantages over fuses: they work ______ and can easily be ______. Words – electromagnet, broken, attract, reset, quicker

25. Multiple Choice Quiz