2. Electricity (electricity in the home & static electricity) Flashcards
What does Alternating current do (AC)?
It repeatedly changes direction and voltage
What is Direct current (DC)?
Current that is always flowing in the same direction. It’s created by a direct voltage
What are the 3 wires in most cables?
- Earth wire
- Live wire
- Neutral wire
What colour is the live wire?
Brown
What colour is the neutral wire?
Blue
What colour is the earth wire?
Green with yellow stripes
What is the voltage of the earth wire?
0v
What is the voltage of the neutral wire?
0v
What does the neutral wire do?
It completes the circuit by carrying current away from the live wire
What is the earth wire and what does it do?
A safety wire, it stops the appliance from becoming live
What does the live wire do?
It provides the alternating potential difference at about 230V from the mains supply
Why can a connection between live and earth wires be dangerous?
The connection creates a low resistance path allowing a lot of current to flow through, causing a spark
What is the equation that links energy transferred, power and time?
E = PT
Energy transferred (J) = power (W) x time (s)
What is a power rating?
The maximum safe amount of energy an appliance can operate at
What is the equation linking energy transferred, charge and voltage?
E = QV
Energy (J) = charge (C) x voltage (V)
What is the equation linking power, voltage and current?
P = VI
Power (W) = voltage (V) x current (A)
What is the equation linking power, current and resistance?
P = I^2 x R
Power (W) = current squared (A) x resistance (ohms)
What is the National grid?
The nationwide network of cables and transformers that connects power stations and consumers
Why is the National grid an efficient way of transferring energy?
As they have a high p.d and decreased current, so less energy is lost through heating
What do step-up transformers do?
Increase the p.d
What do step-down transformers do?
Decrease the p.d
What is static electricty?
- The build up of charge on an insulated object
- When two insulating objects are rubbed against one another, this causes electrons to transfer, from one object to another
- Resulting in a positively charged object and a negatively charged object, that are attracted to one another
What charges are the polythene rod and duster?
- Polythene rod: negatively charged
- Duster: positively charged
What charges are the acetate rod and the duster?
- Acetate rod: positively charged
- Duster: negatively charged
What is an electric field?
A field created around any electrically charged object
What happens when a charged object is brought in the electric field of another object?
A force is felt
Why can static charge cause sparks?
The potential difference between the charged object of 0v can be large enough to create a spark. The potential difference causes a strong electric feild causing ionisation of the air, hence a current can flow through resulting in a spark
What does the positive electric field look like?
What does the negative electric field look like?
