P1: Electricity Flashcards
What is a switch?
Something that is used to turn a circuit on and off.
What is a lamp?
An electrical current heats the filament on a bulb so that it gives out light.
What is a fixed resistor?
A restistor restricts or limits the flow of electrical current. A fixed resistor has a resistance that does not change.
What is a variable resistor?
A resistor whereby the resistance can be changed.
What is a thermistor?
A resistor whereby the resistance changes depending on the temperature.
At low temperatures, what is the resistance like in a thermistor?
High.
Does resistance in a thermistor increase or decrease with temperature increase?
Resistance decreases.
What is a light-dependent resistor?
A resistor whereby the resistance depends on light intensity. At low light levels, the LDR has a high resistance.
In the dark, is the resistance of an LDR high or low?
High.
Does resistance in an LDR increase or decrease as light increases?
Resistance decreases.
What is a diode?
Something that allows current to flow in one direction early. Used to convert an alternating current into a direct current.
What is current?
The rate of flow of electric charge.
What is charge?
The quantity of electricity.
How is current measured?
Using an ammeter.
How is an ammeter placed in a circuit?
In series.
What do you use to measure potential difference?
A voltmeter.
How do you place a voltmeter in a circuit?
In parallel.
Describe the layout of electrical components in a series circuit.
They are connected one after the other in a single loop.
What happens if one bulb goes out in a series circuit?
All of the other bulbs go out as well because current is not able to flow around the circuit.
Describe current in a series circuit.
Current is the same everywhere in a series circuit.
Describe the distribution of potential difference in a series circuit.
The potential different in each component is equal across all of them, and adds up to the total potential difference in the source.
Describe the resistance of a series circuit.
The total resistance of the circuit is the sum of individual resistors.
What happens if one bulb is broken in a parallel circuit?
The current will still be able to flow through the other loops, so all of the others will stay on.
Describe the current in a parallel circuit.
The total current is split between the components on different loops.
Describe the potential difference in a parallel circuit.
The potential difference is the same across each loop, everywhere.
Describe the resistance in a parallel circuit.
The total resistance of the circuit is less than the resistance of the smallest resistor.
What are the types of ways a current can flow?
Direct current and alternating current.
What are the three types of wire in a plug?
Earth wire, neutral wire and live wire.
What is the function of outer insulation in a plug?
Safety.
What is the function of a cable grip in a plug?
Holds the cable tightly in place so that wires do not become loose,
What is the function of a fuse in a plug?
Melts if the current gets too high, protects from excessive current and prevents short circuits.
What colour is the live wire?
Brown.
What colour is the neutral wire?
Blue.
What colour is the Earth wire?
Yellow and green.
Which wire in a plug is brown?
Live wire.
Which wire in a plug is blue?
Neutral wire.
Which wire in a plug is green and yellow?
Earth wire.
What is the function of the live wire in a plug?
Allows the current to enter the plug.
What is the function of a neutral wire in a plug?
Connects to the cable in the wall and completes the circuit.
What is the purpose of the Earth wire in a plug?
Provides a path for current to flow from the case of the device to the ground if there is a fault.
What would happen if a fault occurred making the live wire loose, and there was no Earth wire?
The live wire could touch the case, and the next person who uses the appliance would get electrocuted.
Describe the steps in the National Grid.
Power station —> Step-up transformers —> High voltage transmission lines —> Step-down transformers —> Consumers
What does the National Grid do?
Distributed electricity across the country.
What does a step-up transformer do?
Increases the voltage from 25,000 volts to 400,000 volts.
What does a step-down transformer do?
Decreases the voltage from 400,000 Volts to 230 Volts for home usage.
What is done to the cables in transmission lines to reduce power loss?
-The cables are thick to reduce resistance
-High voltages are used to reduce the current
How can objects that are charged affect other charged objects?
By using the non-contact forces of static electricity.
What is the charge of an electron?
-1
What may happen when insulating material rub against each other?
They may become electrically charged. Electrons will be rubbed off one material and on to the other.
What force gives electrons enough energy to leave the atom and be rubbed off an object?
Friction.
What keeps charge static?
If the electrons can’t move.
What do all charged objects have?
An electric field around them.
What does a Van de Graaff generator do?
Removes electrons to produce a positive charge.
What happens to a charge if an electric field is strong enough?
Charges can be forced through insulators such as air and a spark will occur. (This is what happens during a lightning strike)
