P4,P5 Flashcards
Draw an LDR?
Is it
Draw a diode?
Draw a resistor?
Draw
Draw a bulb?
Bulb
Draw a fuse?
Fuse
Draw a battery?
Battery
Draw a cell?
Cell
Draw a LED?
Led
Draw an ammeter?
Ammeter
Draw a thermister
Thermister
A voltmeter must be placed in a series or a parallel?
Parallel
Describe how a basic transformer is made?
The primary and secondary coil wrapped around an iron core
What is an electric current created chemically?
DC
Example of a use of thermistor?
To turn off the heater when house reaches a certain temperature
Examples of how to create static electricity?
Rubbing ruler/balloon on head
Examples of rectifiers?
Diodes
Explain how the resistance of a filament lamp changes as the potential difference across it?
As the PD across the filament lamp increases current also increases due to ohms law. Current flow also increases the lamp to heat up which causes resistance to as well
Formula for charge,current and time?
Q = It
Charge (c) = current(a) x time(s)
Formula for energy,charge and potential difference?
E = Qv
Energy = Q (coulombs) x V (volts)
Formula for Energy,power and time?
E = Pt
Energy (J) = Power(W) x Time(s)
Formula for power,current and resistance?
P = I^2R
Power = current^2 x resistance
How are electromagnets used in doorbells?
When the bell is pressed the switch is closed. This causes a current flow in the circut. A magnetjc feild is now produced. The iron contact is attracted to the electromagnet. When the contacts moves towards the magnetic feild the clapper hits the bell. Now no current
How can the voltage output from an alternator be doubled?
Double the speed
How can you get an electrostatic shock?
You get it when you are electrically charged and touch something earthed. You get charged by for example walking on carpet
How do loudspeakers and headphones use motor effect?
They convert variations in electrical circuts to pressure variations in sound waves
How do you calculate efficiency?
Output power/input power x 100
How do you calculate the total resistance in a series circut?
Sum of all resistor’s resistance
How does a loudspeaker work?
1) A current in the creates a magnetic field
2) the magnetic field interacts with the permenant magnet generating a force pushing the cone
3) the current is made to flow in the opposite direction
4)direction of magnetic field reverses
5) the force of cone pulls it back
How is a positive static charge caused?
Protons and neutrons cannot move object to object so electrons move elswhere causing less negative charge
In a series circut current is ______ everywhere?
Equal
Is mains electricity AC or DC?
AC
Voltage of UK mains supply?
230V
What can be said about electrical power input and output of an effecient transformer?
Power input = power output
What does a diode do?
Allows current to flow in one direction
What does a dynamo use the generator effect for?
To generate direct current
What does a stepdown transformer do?
Increases the current and lowers the voltage
What does a thermistor do?
Resistance changes with temperature
What does an ammeter do?
Measure the current in amps flowing through a wire. An ammeter must be placed in a series
What does more energy effecient mean?
A higher percentage of the energy is transfered
What does the natural grid consist of?
Cables and transformers
What electromagnetic effect does a microphone take advantage of?
- The generator effect
What happens if a component in a series breaks?
Entire circut is broken and they all stop
What happenes if the resistance increases?
The smaller the current flows
What happens if you add a resisitor or component in parallel circut?
The resistance decreases as more components are added because there are more paths to go through
What happens to the current in a parallel circut?
Shared between components
What happens when a electrical conductor moves to a magnetic field?
A potential difference is induced across the ends of a conductor
What is a rectifier?
Something that turns alternating current into direct current
What is a step up transformer?
Increase voltage reduce current
What is an alternating current?
Constantly changes direction
What is an electric field?
A region where a charged object will experience a non contact electrical force
What is an ohmic conductor?
A conductor which Obeys ohms law
What is charge?
The amount of current passing through a certain point in a certain amount of seconds
What is direct current?
Current flowing in same direction
What is electric current?
Flow of electric charge
Whats is ohms law?
Voltage is directly proportional to current flowing through it
Hat is potential difference measured in?
Volts
What is potential difference?
How much energy is transfered between two points in a circut
What is resistance measured in?
Ohms
What is resistance?
Measure of oposition to current flow in electrical circut
What is rotated by an energy force to produce electricity by generator effecf?
Turbine
What is static electricity?
The result of imbalance between negative and positive charges in a object
What is the earth wire used for?
To protect wire amd stop appliance from being live
What is the frequency of electricity supply in uk?
50hz
What is the function of a microphone?
Converts sound waves in electrical signals
What is the live wire?
Transfers electricity to appliance
What is the national grid?
A giant system of cabels and transformers that covers the uk and connects power station to consumers
What is neutral wire used for?
- Completes the circut and carries away current
- electricity normally flows through a live wire and out through a neutral wire
Whats the purpose of a fuse in a circut?
The fuse breaks a circut if the appliance causes too much current to flow
What is the requirement for an indiced potential differenceto cause current flow?
Current must form a closed loop
What is the unit for current?
Amps
What remains constant in ohmic conductor?
Resistance
What type of conductor is a fixed resistor?
Ohmic conductor
What are parallel circuts mostly used in?
Houses
Why do solar pannels on homes help reduce enviromental impact?
Less fossil fuel burned
Why does a van de gaaf generator make ur hair stand up?
Each strand of hair picks up the same haie and repels each other
Why does natural grid use transformers?
High current makes you lose loads of energy. It is cheaper to boost high voltage and keep current low
How can closing the switch affect the variable resistor?
Current will be 0 because switch has 0 resistance
Advantage of transmiting electricity at a high potential differenece?
- Low currents
- Less thermal energy transfered
Why is it a person holding a kite near a power cable get an electric shock?
- electric field strength is high
- Causing air to become ionised
Explin why current in a steel wire is different to an aluminium wire?
Pd is same but steel wire resistance is greater
Why is it when an electrician touches a live wire they receive an electric shock?
- The Pd of the wire is 230v
- The pd of the person is 0v
- large pd between two
- current passes through body
How does the current on a thermistor depend on the tempeature?
As the current increases so does the temperature
