MIGHT COME UP IN EXAM??? Flashcards
What does the neutral wire do?
Completes the circuit
0V
What colour is the neutral wire?
Blue
What does the earth wire do?
Stops the appliance case from becoming live
0V
How does the earth wire make the plug safe?
Carries current to the ground
A large current flows in the earth wire which causes the fuse to melt so protects the user from an electric shock
What colour is the earth wire?
Green and yellow
What does the live wire do?
Provides the alternating potential difference
230V
What would happen if a human touched the live wire?
They would receive and electric shock
Why would you receive an electric shock if you touch a live wire?
Because it creates a large potential difference between you (earthed so 0V) and the live wire (230V)
So a current flows through you
What is the national grid?
Giant system of cables and transformers that connects power stations to consumers
Why do power stations run at below their maximum power output?
So there is spare capacity to cope with a high demand
Why do you lose energy if you have a high current?
Because the wires heat up causing energy to be lost to thermal energy stores
Why is it better to increase the potential difference in the national grid than the current?
Cheaper
More efficient as less energy is lost
What is the order of atomic structure in names?
Dalton
Thomson
Rutherford
Bohr
Chadwick
What is the order of discovery of the atom?
Ball model
Plum-pudding model
Nuclear model
Planetary model
Neutrons
What is the plum-pudding model?
Ball of positive charge with negative electrons stuck in it
What is the nuclear model?
Positive nucleus surrounded by negative electrons
What is the planetary model?
Positive nucleus with electrons orbiting it in shells
How does a moving charge transfer energy?
The charge does work against the resistance of the circuit
What is an example of energy not being transferred usefully?
The higher the current the more energy transferred to thermal energy stores
What is a power rating?
The maximum safe power that the appliance can operate at
What does the power rating show?
The maximum amount of energy transferred between stores per second
Why is it good if an appliances power rating is low?
The lower the power rating the less electricity an appliance uses so it is cheaper to run
What does a higher power output not mean?
Doesn’t mean it transfers more energy
May be more powerful but less efficient so still transfers the same amount of useful energy as another appliance with a lower power output
What is fission?
When a large atomic nuclei splits to form two smaller nuclei
How does fission occur?
A neutron is absorbed into a nuclei which causes the nuclei to become unstable and split
What is also produced during nuclear fission?
Two or three more neutrons which can collide with other nuclei to cause further fission reactions - chain reaction
What is fusion?
When two small, light nuclei join together to make one heavy nucleus
Why does mass decrease in nuclear fusion?
The missing mass is converted to energy, which radiates away
What is gas pressure caused by?
Caused by the collisions between the particles and their container
What happens in a filament lamp?
Current increases as potential difference does
So temperature of the wire increases
Therefore harder for current to flow through resistor
So resistance increases
What does increasing the temperature increase the resistance?
Causes greater vibrations in the ions of the wire so harder for electrons to get past
What happens when a current flows through a diode?
Can only flow in one direction
Because if potential difference flows the wrong way, the resistance is too high so no current will flow
