Electricity-Paper 1
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What is current
Current is the rate of the flow of charge
What is potential difference
Energy per unit charge
What is a series circuit
One path for current to flow
What is a parallel circuit
More than one path for the current to flow
How does current behave in a series circuit
Same value at any point
How does Potential difference act in a series circuit
Shared PD added up is the same is the PD from the source
Effect of adding a resistor in series
Total resistance is increased
How does current behave in a Parallel circuit
The current is shared between branches
How does potential difference behave in a parallel circuit
The PD is the same across all components
What is the effect of adding a resistor in a parallel circuit
Reduced the total resistance
What does an I-V graphic show
Shows how the current flowing through a component changes as the potential difference across it increases
What is a national grid
A system of cables and transformers that connects power stations to consumers
Describe the I-V graph of an ohmic conductor
The current through an ohmic conductor at constant temperature is directly proportional to the potential difference
Describe the I-V graph it a filament lamp
As the current increased the temperature of the filament lane increases The atoms in the filament vibrate more Resistance increases
Describe the I-V graph of a diode
Current will only flow through a diode in one direction The diode has a very high resistance in the opposite direction
What is a LDR
A resistor that depends on light
What is a thermistor and the effect on heat on resistance
A resistor that depends on temperature The higher the temperature the lower the resistance
Describe mains electricity
Mains electricity is an AC supply Frequency of 50Hz PD of 230v
What happens to the current and PD in a step up transformer and step down
Step up:PD increases Current Decreases Stepdown:Opposite
Why does the National grid use transformers
Lowers the current to reduce any heating of the transmission cables This means PD has to increase Reduce PD after to make it safe for consumers
What is an electrical field
A region around a charged object where there can be a non contact force
What forces occur between charged objects
Non contact forces occur between charged objects Opposite charges attract each other
What is static electricity
When two different insulators are rubbed together Electron may transfer from one material to another A positive Static electricity forms when an object loses electrons A negative Static electricity forms when an object gains electrons
How can you discharge an object to prevent sparking
By being earthed