Physics (GCSE) Revision (Electricity)
Quiz yourself by thinking what should be in
each of the black spaces below before clicking
on it to display the answer.
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| A current will flow through an electrical component only if there is . . . | show | Potential difference makes charges flow
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| The bigger the potential difference across a component . . . | The bigger the CURRENT that flows through it. | show 🗑
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| Components resist a current flowing through them. The bigger their resistance . . . | show | This is like squeezing a garden hose - it restricts the flow of water
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| The p.d. across a component in a circuit is measured in . . . | VOLTS | show 🗑
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| Voltage (p.d.) is measured using . . . | a VOLTMETER connected IN PARALLEL with the component. | show 🗑
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| show | an AMMETER connected IN SERIES with the component. | You need to put the ammeter in line with the current so it flows through the meter
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| The unit of current is . . . | the AMPERE (AMP) | show 🗑
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| A current of 1 A is equal to a charge flowing of . . . | show | 1 coulomb is a really BIG number of electrons
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| In metals, a current is a flow of charged particles called . . . | ELECTRONS | show 🗑
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| In a circuit, we say that CURRENT always flows from . . . | show | Red is positive - black is negative
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| In metals, electricity is actually carried by NEGATIVELY charged electrons, which flow from . . . | show | This was a mistake made over 100 years ago when they didn't know about electrons !
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| The behaviour of a component in a circuit can best be studied by plotting . . . | a current-voltage graph. | show 🗑
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| A resistor at constant temperature has a constant ratio of . . . | current to voltage. Its graph is a straight line. | show 🗑
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| The current-voltage graph for a filament lamp is NOT a straight line. The reason is . . . | show | The graph is a curve - current stops increasing at quickly because it gets harder for it to flow through the higher resistance
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| A diode is a device which . . . | show | The graph shows a sudden rapid rise in current when the p.d. exceeds 0.7 volt ( but in reverse the current is just zero )
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| When components are connected in series . . . | show | There is nowhere else for it to go
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| The total resistance of components in series is . . . | equal to the SUM of their separate resistances. | show 🗑
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| show | shared between the individual compoents. | You only have so much pocket money to spend . . .
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| If a p.d. of 12 volts is shared between two equal resistances, each one will get . . . | show | If the same current flows in each, the voltage is proportional to the resistance
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| If a p.d. of 12 volts is shared between two resistors of 6 ohms and 12 ohms, the bigger resistor will get . . . | show | Voltage is directly proportional to resistance according to Ohm's Law
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| When components are connected IN PARALLEL . . . | show | Think of the rungs on a ladder - they are all connected in parallel between the two uprights
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| The total current in a parallel circuit is equal to . . . | the SUM of the currents through each of the separate components. | show 🗑
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| If one lamp is connected to a cell it gets a current of 1 amp. If two identical lamps are connected in parallel (to the same cell) they will get . . . | show | You can put as many lamps in parallel as you like and they will all get 1 amp each
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| If one lamp gets a current of 1A from one cell, two lamps joined in series will get . . . | show | Three lamps get 1/3 amp, etc.
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| The p.d. provided by cells connected in series is equal to . . . | the SUM of the p.ds. of each cell separately bearing in mind the direction in which they are connected. | show 🗑
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| How many different p.ds. can you get from 4 cells, each of 1.5volts, connected in series? | THREE ( 6v, 3v, 0v) | show 🗑
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| The resistance of a component is measured in | show | 1 ohm is 1 volt per amp
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| Potential difference, current and resistance are related by Ohm's Law which states | show | V = IR (if you want to save ink)
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| show | R = p.d. / current | R = V / I (always put V on top)
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| show | 20 volts | V= IR = 2x10 = 20 v
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| What is the current when a p.d. of 12v is applied across a 10 ohm resistor? | show | I = V/R = 12/10
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| show | directly proportional to the p.d. across the resistor. | A graph of current against voltage would be a straight line which passes through the origin
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| show | decreases as the light intensity increases. | They are used to switch on street lights at dusk
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| show | decrease as the temperature increases. | Can be used as a thermostat to control central heating
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| show | energy is transferred from the battery or power supply to the components in the circuit. | A battery is a source of electrical energy which can easily be converted into more useful forms such as light, heat and sound
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| A lamp converts electrical energy into . . . | show | More light than heat - especially if energy efficient lamps are used
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| When electric charge flows through a resistor, electrical energy is transferred as . . . | HEAT | show 🗑
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| The rate of energy transfer is called . . . | POWER | show 🗑
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| Power is measured in watts. 1W is equal to . . . | 1 joule per second | show 🗑
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| show | current x potential difference | P = I V ( Pretty Impressive Victory )
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| Energy transferred = | show | E = P x t ( Eeeeh, Poor Thing ! )
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| CHARGE = | show | Q = It ( Quit - while you're ahead )
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| The higher the p.d. the greater the energy transferred for a given amount of charge which flows. Energy transferred = | show | E = Q V ( Eastenders Queen Victoria )
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| show | Direct current | What else ?
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| The letters A.C. stand for . . . | Alternating current | show 🗑
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| show | a cell or battery ( or dc power supply) | An ac supply can be made into dc by using diodes
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| A direct current is one in which . . . | show | For example, in a solution of copper sulphate
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| An alternating current is one which flows . . . | first in one direction then in the opposite direction alternately. It is constantly changing. | show 🗑
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| The frequency of alternating current in the UK is . . . | 50 Hertz ( or cycles per second) | show 🗑
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| The voltage of the UK mains supply is . . . | show | It used to be 240v but what with inflation . . .
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| show | BROWN | You'll know what this means if you touch it !
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| In Europe, the earth cable is coloured . . . | GREEN & YELLOW | show 🗑
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| In Europe,the neutral wire in a 13A plug is coloured . . . | BLUE | show 🗑
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| If a fault occurs in an electrical circuit the current is interrupted by a . . . | FUSE (or circuit breaker) | show 🗑
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| show | the current exceeds the value of the fuse e.g. 5amp. | Don't say fuse 'blows' - it's rude !
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| Fuses and circuit breakers should always be fitted in the . . . | LIVE wire | show 🗑
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| show | the current can flow to earth preventing the user from receiving a shock. | If you touch a LIVE metal case, the current will flow through YOU to earth - not nice !
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| It is safe to use an appliance fitted with a 2-pin plug because . . . | show | e.g. a hairdryer with a plastic case and handle
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| A loudspeaker converts electrical energy into . . . | show | Don't abbreviate loudspeaker to 'speaker'
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| show | electrical energy. | Testing, testing . . . 1, 2, 1, 2, etc.
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| A motor converts electrical energy into . . . | show | e.g. an electric drill
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| A dynamo converts kinetic energy into . . . | show | On a bicycle
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| The amount of electrical energy transferred from the mains is measured in units called . . . | show | That's kilowatts x hours
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| 1 kWh = | show | 1000 W x 3600 seconds = 3 600 000 joules
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| show | Number of units (kWh) x cost per unit | Roughly 8p per unit (kWh)
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| show | Cost = 0.5 x 6 x 8 = 24p | Convert to kilowatts and hours first
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| Metals are good conductors of electricity because . . . | some of their electrons can move freely throughout the metal. | show 🗑
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| When a current flows through a solution the process is called . . . | electrolysis | show 🗑
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| In an electrolyte, current is carried by charged particles called . . . | IONS | show 🗑
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| Positve ions move towards the . . . | show | cat means 'down' in Greek (apparently)
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| Negatively charged ions move towards the . . . | ANODE | show 🗑
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| During electrolysis the mass or volume of the substance deposited or released at the cathode depends on . . . | the current and the time for which it flows. | show 🗑
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| A capacitor is a device which is used to store . . . | show | Rechargeable batteries derived from electrolytic capacitors
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| A capacitor takes time to charge up or to discharge. This can be used in . . . | a timing circuit | show 🗑
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| When two different materials are rubbed together . . | electrons are transferred from one to the other | show 🗑
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| show | they do not conduct electricity | Their electrons are tightly bound to the atoms
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| When a substance loses electrons, it becomes . . . | show | Double negative : minus minus equals plus
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| Opposite electric charges will . . . | ATTRACT each other | show 🗑
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| Like charges . . . | REPEL each other | show 🗑
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| show | connecting it to EARTH with a conductor | The Earth acts like a bank - you can pay in or take out whatever you want
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| show | a copying plate which conducts when light shines on it | You need to read up on this
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| show | an electrostatic precipitator | This is a great idea - make sure you know how it works
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| When walking along a nylon carpet with plastic-soled shoes, you may pick up a static charge. This happens because . . . | electrons are transferred by friction from the shoes to the carpet | show 🗑
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| When you touch a metal door handle you sometimes receive an electric shock because . . . | a charge passes from your body to earth through the door handle | show 🗑
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| When filling a car with petrol, the nozzle should make good electrical contact with the neck of the tank. This is to prevent . . . | show | Aircraft need to be connected to the tanker by a metal bonding line for the same reason
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Created by:
J Thomson
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