Topic 2 Higher Flashcards
(19 cards)
What happens to the total resistance and current in a parallel circuit?
The total resistance decreases and the current increases as there are multiple pathways
When there are 2 resistors in parallel what is the total resistance of the circuit?
The total resistance is less than the resistance of the smallest resistor
What is the role of a diode?
To control the direction of current
Explain how resistance changes in a filament lamp.
As the voltage and current increases the wire begins to heat up
The rise in heat causes the atoms in the wire to vibrate leading to the resistance increasing
How does temperature affect resistance
The higher the temperature the higher the resistance
Explain static.
Two insulating materials rub together
This leads to the transfer of electrons
The material that looses electrons becomes positively charged
The material that gains electrons becomes negatively charged
The two materials are attracted to one another as opposite charges attract
What is used to increase the voltage from power stations to the mains electricity?
A step up transformer
What is used to decrease the voltage from mains electricity to domestic wires
Step down transformers
How do you calculate total resistance in a series circuit?
Add together the resistance of each component
How do you calculate the total voltage in a series circuit?
The sum of the PD across each component
What do we know about he current around a series circuit?
The current is the same anywhere around the circuit
How do you calculate the total voltage in a parallel circuit?
The potential difference is the same all the way around the circuit
How do you calculate the total current around a parallel circuit?
The sum of the current through each branch
What color is the live wire ?
Brown
What color is the neutral wire
Blue
What color is the earth wire?
Green and yellow stripes
What is the danger if the live wire becomes loose?
- the live wire may touch the metal casing of the appliance
- this may cause the casing to become live
- if a person is close to the casing they may get an electric shock
What is the purpose of the earthed wire?
If the live wire touches the causing the earth wire directs the voltage into the ground reducing risk of electric shock
When does a spark occur?
- ehen an object becomes significantly charged it creates an electric field around the object.
- this strong electric field can pull electrons from air particles causing the air to become ionized
- this allows current to flow through the air
