Practical Electricity

Name: Practical Electricity
Uploaded: 2017-07-18T05:41:07+00:00
Duration: PTM42S15
Channel: Janice Horton
Description: Practical Electricity

Practical Electricity
Intermediate 1 Physics Practical Electricity Electrical Circuits Resistance Mains Electricity Beath High School - Int 1 Physics

Intermediate 1 Physics Practical Electricity Electrical Circuits Beath High School - Int 1 Physics

Beath High School - Int 1 Physics
Electrical Circuits A circuit will always have, a source of e _ _ _ _ _ _ _ _ _ energy an electrical comp _ _ _ _ t wires forming a c _ _ _ _ _ _ _ path from one end of the source back to the other end. electrical onent complete Beath High School - Int 1 Physics

Electrical Circuits If the circuit is c _ _ _ _ _ _ _ , there will be current. If the circuit is incomplete, there will be no c _ _ _ _ _ _ . complete current. Beath High School - Int 1 Physics

Circuit Symbols Each electrical component has a symbol - called a "circuit symbol". When we draw circuit diagrams, we draw the circuit symbol instead of trying to draw the component itself. The following table is a list of the circuit symbols for all the electrical components needed for this course as well as a brief description of the function of the component. Beath High School - Int 1 Physics

Circuit Symbols 1 Component Symbol Description Battery supplies electrical energy Converts electrical energy into light energy lamp Open: breaks a circuit Closed: completes a circuit switch Beath High School - Int 1 Physics

Circuit Symbols 2 Component Symbol Description converts electrical energy into _ _ _ _ energy heater heat Opposes current; it converts electrical energy into heat resistor variable resistor A resistor whose resistance can be changed Beath High School - Int 1 Physics

Circuit Symbols 3 Component Symbol Description Converts electrical energy into kinetic energy M Motor A Used to measure electric current – always connected in series Ammeter V Used to measure voltage – always connected in parallel Voltmeter Beath High School - Int 1 Physics

Circuit Symbols 4 Component Symbol Description Measures resistance directly – use when the component is not connected. W Ohmmeter A protection device. It melts when the current gets too high. Fuse Beath High School - Int 1 Physics

Series Circuits When components are connected to allow only one path for the current, we say that the components are connected in series. three l _ _ _ _ in series lamps A lamp, ammeter and fuse connected in series. Beath High School - Int 1 Physics

Series Circuits If the components form a circuit, the circuit is called a s _ _ _ _ _ circuit. series A series circuit. The battery, switch, lamp, variable resistor and ammeter are all connected in series. There is only o _ _ path for the c _ _ _ _ _ _ from one end of the battery, through each component in turn to the other end of the battery. A one current Beath High School - Int 1 Physics

Parallel Circuits When components are connected to allow m _ _ _ than one path for the current, we say that the components are connected in parallel. more two lamps in p _ _ _ _ _ _ _ parallel Beath High School - Int 1 Physics

Parallel Circuits lamp, heater and voltmeter connected in parallel. V Beath High School - Int 1 Physics

Parallel Circuits A parallel circuit. The b _ _ _ _ _ _ , lamp and voltmeter are all connected in p _ _ _ _ _ _ _ . V battery parallel. There is more than one separate path for the c _ _ _ _ _ _ . You can trace a separate path from the b _ _ _ _ _ _ through either component back to the o _ _ _ _ end of the battery. current battery other Beath High School - Int 1 Physics

Measuring Current Current is measured using an a _ _ _ _ _ _ ammeter Current is measured in amperes (a _ _ _ ). (The shorthand for amperes is ‘A’) amps To measure the current through a component, always connect the ammeter in s _ _ _ _ _ with the component. This means b _ _ _ _ _ _ _ the circuit to insert the ammeter. series breaking Beath High School - Int 1 Physics

Measuring Current Connecting an ammeter A After Before The circuit is altered to include the ammeter in series with the lamp. The reading on the ammeter is the current t _ _ _ _ _ _ the lamp. through Beath High School - Int 1 Physics

Measuring Voltage Voltage is measured using a voltmeter Voltage is measured in v _ _ _ _ . volts (Shorthand for volts is ‘V’) To measure the voltage across a component, always connect the voltmeter in p _ _ _ _ _ _ _ with the component. parallel The voltmeter forms another parallel branch across the component. Beath High School - Int 1 Physics

Measuring Voltage Connecting the voltmeter V Before After The voltmeter is added to make another branch in p _ _ _ _ _ _ _ with the lamp. parallel The reading on the voltmeter is the voltage across the l _ _ _ . lamp. Beath High School - Int 1 Physics

Current and Voltage in Series Circuits
The current through every component in a series circuit is i _ _ _ _ _ _ _ _ and is the same as the supply current. identical A To measure the current in each lamp, connect an ammeter in s _ _ _ _ _ with each lamp. series Each ammeter will have the s _ _ _ reading. same Beath High School - Int 1 Physics

The sum of the voltages across each component in a series circuit adds up to the supply voltage. The voltage across each lamp can be measured directly. Beath High School - Int 1 Physics

This voltmeter measures the voltage a _ _ _ _ _ the battery. This is the supply voltage. across V V V To measure the voltage across each lamp, connect a voltmeter in parallel with each lamp. The voltmeter readings across the lamps a _ _ up to the supply voltage. add Beath High School - Int 1 Physics

Examples 1. In the circuit shown, the current reading on one of the ammeters is 0.2 amperes. Find the current reading on the other ammeter and the current through each lamp. A 6V 0.2A In a series circuit, the current is the s _ _ _ at all points. same The current reading on the other ammeter = A also the current through each lamp = A 0.2 0.2 Beath High School - Int 1 Physics

Examples 2. Find the supply voltage in the circuit shown below. V 1V 2V In a series circuit, the voltages across each component add up to the supply voltage. The supply voltage = 2 + 1 = V 3 Beath High School - Int 1 Physics

Current in parallel circuits
The sum of the currents through each component in a parallel circuit adds up to the supply current. The current through each lamp and the battery can be measured directly. Beath High School - Int 1 Physics

To measure the current in each lamp, connect an ammeter in s _ _ _ _ _ with each lamp. series Beath High School - Int 1 Physics

This ammeter measures the c _ _ _ _ _ _ through the battery This is the supply current. A To measure the current in each lamp, connect an ammeter in s _ _ _ _ _ with each lamp. series To measure the current through the battery, connect an a _ _ _ _ _ _ in series with the battery. ammeter The ammeter readings a _ _ up to the ammeter reading of the current through the supply. add Beath High School - Int 1 Physics

Voltage in parallel circuits
The voltage across every component in a parallel circuit is i _ _ _ _ _ _ _ _ and is the same as the supply voltage. identical The voltage across each lamp can be measured directly. Beath High School - Int 1 Physics

This v _ _ _ _ _ _ _ _ measures the voltage across the battery. This is the supply voltage. voltmeter V Beath High School - Int 1 Physics

To measure the voltage across each lamp, connect a voltmeter in p _ _ _ _ _ _ _ with each lamp. a r a l l e l V Each voltmeter will have the s _ _ _ reading. a m e The supply voltage is the s _ _ _ as the voltage across each lamp. V a m e Beath High School - Int 1 Physics

Intermediate 1 Physics Practical Electricity Resistance Beath High School - Int 1 Physics

Resistance Materials oppose current and some materials oppose it more than others. The opposition to current is called r _ _ _ _ _ _ _ _ _ . e s i s t a n c e An increase in resistance causes a d _ _ _ _ _ _ _ in current. e c r e a s e Beath High School - Int 1 Physics

Resistance A resistor causes electrical energy to be converted into h _ _ _ energy in the material. Sometimes this is a nuisance – when circuits heat up and get too h _ _ . Sometimes it is useful – when heat is required, for example in k e t _ _ _ _ or cookers. e a t o t t l e s Beath High School - Int 1 Physics

Measuring Resistance Resistance is measured in o _ _ _ . h m s (Shorthand for ohms is “W” – the Greek letter omega) Resistance can be measured using an o _ _ _ _ _ _ _ . h m m e t e r To measure resistance, connect the ohmmeter directly across the resistor or component whose resistance you want to measure (nothing else connected). W Beath High School - Int 1 Physics

Calculating resistance from ammeter and voltmeter values
Put the resistor or component into a circuit. Measure the current through the resistor by connecting an a _ _ _ _ _ _ in s _ _ _ _ _ . m m e t e r e r i e s A Beath High School - Int 1 Physics

Put the resistor or component into a circuit. Measure the voltage across the resistor, connecting a v _ _ _ _ _ _ _ _ in parallel. o l t m e t e r A V Beath High School - Int 1 Physics

Calculate resistance using: resistance = voltage current A V Beath High School - Int 1 Physics

Calculate resistance using: resistance = voltage current Example: The current through a resistor is 0.1 amperes when the voltage across it is 12 volts. Calculate the resistance. V A voltage current 12 0.1 = resistance = = 120W Beath High School - Int 1 Physics

Variable resistors It is often useful to be able to adjust the flow of current continuously. For example; controlling the loudness or brightness of a TV, the heat setting on a toaster, adjusting the speed of a model train. To do this we use a v _ _ _ _ _ _ _ resistor; symbol: a r i a b l e When the resistance is reduced, the current i _ _ _ _ _ _ _ _. n c r e a s e s Beath High School - Int 1 Physics

Intermediate 1 Physics Practical Electricity Mains Electricity Beath High School - Int 1 Physics

MAINS ELECTRICITY Safety Note: Mains electricity is dangerous. Never experiment with mains electricity. Electricity supplied to houses is called m _ _ _ _ electricity. a i n s Mains electricity is dangerous because your body can c _ _ _ _ _ electricity and mains voltage can cause a current large enough to k _ _ _ you. o n d u c t i l l Your body conducts even m _ _ _ if it is wet or damp, this is the reason why there must be no sockets or switches in a _ _ _ _ room. o r e b a t h Beath High School - Int 1 Physics

MAINS ELECTRICITY The declared value of mains voltage is _ _ _ volts 2 3 0 All mains a _ _ _ _ _ _ _ _ _ in Britain are designed to operate with a voltage of 230 volts across them. p p l i a n c e s This means that the household wiring must be such that all the appliances are connected in p _ _ _ _ _ _ _ . a r a l l e l This ensures that each appliance receives the same voltage (230V). Beath High School - Int 1 Physics

The three pin plug Household wiring consists of cables in which there are t _ _ _ _ wires. h r e e The cable is connected to the m _ _ _ _ using a three pin plug – one pin for each of the wires. a i n s Beath High School - Int 1 Physics

The three pin plug 1. The live wire (b _ _ _ _ ) r o w n The live wire is the wire connected to the 230 volts supply from the p _ _ _ _ station. It is coloured b _ _ _ _ . If you touch the brown wire of an appliance which is connected to the mains you will get a s _ _ _ _ which can kill you. The switch in an appliance is always connected to the l _ _ _ wire so that when the switch is off, the appliance is dis _ _ _ _ _ _ _ _ _ from the 230 V supply from the mains. o w e r r o w n h o c k i v e c o n n e c t e d Beath High School - Int 1 Physics

The three pin plug 2. The neutral wire (b _ _ _ ) l u e The neutral wire is used to complete the circuit from the appliance to the mains. If you touch the blue wire in an appliance you can still get a shock if the appliance is connected to the m _ _ _ _ and working. a i n s Beath High School - Int 1 Physics

The three pin plug 3. The earth wire (g _ _ _ _ and y _ _ _ _ _ ) r e e n e l l o w The earth wire does not normally carry c _ _ _ _ _ _ . It is a s _ _ _ _ _ device. It only carries current if there is a f _ _ _ _ in the appliance. All appliances with metal parts which can be touched must have an e _ _ _ _ wire. u r r e n t a f e t y a u l t a r t h Beath High School - Int 1 Physics

Double Insulated appliances
Appliances are called "double insulated" if it is impossible to touch the l _ _ _ wire inside it. These appliances do not need an e _ _ _ _ wire and only have a live and neutral wire. Double insulated appliances have this symbol on them. i v e a r t h Double insulated symbol. Appliances with this symbol do not have an earth wire since it is impossible to touch any m _ _ _ _ parts. e t a l Beath High School - Int 1 Physics

Wiring a plug All appliances are connected to the mains power supply by a three pin p _ _ _ . The plug which connects an appliance to the mains must be connected as shown: l u g e a r t h y e l l o w b r o w n u s e b l u e cable grip n e u t r a l l i v e Beath High School - Int 1 Physics

Wiring a plug It is d _ _ _ _ _ ous to operate an appliance if the wires are not connected as shown here. If you are unsure about a plug’s wiring, do not use it! a n g e r e a r t h y e l l o w b l u e n e u t r a l l i v e u s e b r o w n cable grip Beath High School - Int 1 Physics

The fuse The fuse in a plug is a s _ _ _ _ _ device to protect the c _ _ _ _ . It melts if the current in the cable gets too h _ _ _ . All plugs contain a fuse. The fuse is always connected between the l _ _ _ pin of the plug and the l _ _ _ wire of the appliance. This is so that if something goes wrong, the fuse m _ _ _ _ and disconnects the live wire of the appliance from the m _ _ _ _ power supply. a f e t y a b l e i g h i v e i v e e l t s a i n s Beath High School - Int 1 Physics

Fuse values Fuse values are usually 3 a _ _ _ _ _ or 13 a _ _ _ _ _ in domestic appliances. It is important to use the correct fuse values to avoid too high a c _ _ _ _ _ _. The fuse value can be calculated from the v _ _ _ _ _ _ and the p _ _ _ _ rating: m p e r e m p e r e u r r e n t o l t a g e o w e r current = power voltage Beath High School - Int 1 Physics

Fuse values Example: Calculate the fuse value required for a mains appliance with a power of 1150 watts. current = power voltage 1150 = = 5A 230 Therefore a ______ ampere fuse is required. 13 As a general rule if the power rating is 700 W or more, a 13 ampere (13 A) fuse must be used. If the power rating is less than _____ W a 3 ampere (3 A) fuse must be used. 700 Beath High School - Int 1 Physics

Electrical Power Electrical energy is not free! We have to p _ _ for batteries to get electrical energy from them and we have to pay for the electrical energy supplied by the p _ _ _ _ station. The amount of energy used by a household is measured by the m _ _ _ _ at the consumer unit. a y o w e r e t e r Beath High School - Int 1 Physics

Electrical Power Every appliance has a p _ _ _ _ rating marked on it (usually in kilowatts kW, or watts W). The greater the power of the appliance, the more/less energy it uses in one second (this is because it uses more/less current). Also, the longer the time the appliance is used, the more/less energy it uses. So to save energy and money, always switch o _ _ appliances after use. o w e r f f Beath High School - Int 1 Physics

The Consumer Unit Mains electricity comes from the power station into your house through a service cable which goes to the m _ _ _ _ board. e t e r Beath High School - Int 1 Physics

The Consumer Unit From here the mains supply is split into various domestic c _ _ _ _ _ _ _ . The lights, power sockets and cooker each have s _ _ _ _ _ _ _ circuits which are wired in p _ _ _ _ _ _ _ . The parallel wiring ensures each circuit has the same _____ V voltage needed to operate appliances. i r c u i t s e p a r a t e a r a l l e l 230 Beath High School - Int 1 Physics

Mains Protection Although the fuse in the three pin plug protects the cable of the appliance, it does not protect any wiring in the house which comes from the mains supply (wires behind the w _ _ _ _ , etc.). a l l s Beath High School - Int 1 Physics

Mains Protection Household wiring is protected at the point where it comes into the house - at the consumer unit. Every circuit in the house is protected in the mains consumer unit. In older houses, a f _ _ _ is used to protect each circuit but in newer houses and houses which have been recently rewired, a circuit b _ _ _ _ _ _ is used. u s e r e a k e r Beath High School - Int 1 Physics

The circuit Breaker A circuit breaker is a very fast s _ _ _ _ _ which opens and disconnects the circuit when the current gets too l _ _ _ _ . It disconnects the circuit by switching faster than a f _ _ _ can by melting. This means that c _ _ _ _ _ _ breakers are much safer and are gradually replacing fuses altogether. w i t c h a r g e u s e i r c u i t Beath High School - Int 1 Physics

Using Extensions When appliances are plugged into an extension block, the total current i _ _ _ _ _ _ _ _ . A kettle carries a current of about 10 amperes. If four kettles were to be plugged into an extension block, the total current being carried would be about ____ amperes. This very high current causes the cables behind the wall or under the floor, to h _ _ _ up and become a f _ _ _ risk. Unfortunately, this is the cause of many house fires. n c r e a s e s 40 e a t i r e Beath High School - Int 1 Physics

Some Safety Rules 1. Never use worn or damaged flexes: you could get a s _ _ _ _ from an exposed live wire. h o c k 2. Avoid the use of extensions if possible: too many appliances connected to an extension could produce o _ _ _ _ _ _ _ _ _ _ at the socket. v e r h e a t i n g Beath High School - Int 1 Physics

Some Safety Rules Always use the correct flex: a flex which is too t _ _ _ could overheat. h i n 4. Always use the correct plug fuse: if the fuse rating is too high and a f _ _ _ _ develops, the flex could overheat. a u l t Beath High School - Int 1 Physics

Testing for Continuity
Simple conductors can be tested for continuity by trying to pass a c _ _ _ _ _ _ through them in series with some indicator device (e.g. a b _ _ _ or ammeter). u r r e n t u l b If there is a current, the series circuit is c _ _ _ _ _ _ _ . If there is no current, there is a b _ _ _ _ in the circuit. o m p l e t e r e a k Beath High School - Int 1 Physics

Switches can be tested, after removing them from their circuit, by using this simple continuity tester. There should be a current with the switch in the O _ position. There should be n _ current when the switch is changed to the OFF position. N o Beath High School - Int 1 Physics

The continuity tester must never be used with equipment connected to the mains! This simple continuity tester should not be used for components which are still c _ _ _ _ _ _ _ _ in their circuits. o n n e c t e d Beath High School - Int 1 Physics

Using a multimeter When using the multimeter to test for faults, set the multimeter to measure r _ _ _ _ _ _ _ _ _ and place the probes across the component or circuit element. If the reading is infinity ( a " 1 " shows on the left of the display) there is an o _ _ _ circuit (this is O.K. if you are testing a switch set to OFF). If there is a reading, the circuit is c _ _ _ _ _ _ _ . e s i s t a n c e p e n o m p l e t e Safety Point You must only test a component if there is no chance of there being any current in it. Beath High School - Int 1 Physics

Intermediate 1 Physics Practical Electricity End of Unit Beath High School - Int 1 Physics

Practical Electricity

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