P2 Electricity

Question 1

What is electric current

Answer 1

The flow of electrons

Question 2

What is the point of step up transformers

Answer 2

They increase potential difference and decrease current. As higher currents lose more energy as heat is transferred to surroundings

Question 3

What is the point of step down transformers

Answer 3

They decrease the potential difference from the national grid to the consumers so that the 230V is safe for consumers

Question 4

What does the national grid consist of

Answer 4

Cables/Transformers/Power stations

Question 5

What is the frequency and potential difference of the UK’s electrical mains.

Answer 5

50Hz
230V

Question 6

What are the 3 wires in a Uk plug and explain their purpose

Answer 6

Live-Brown- 230V and carries the alternating potential difference from the supply. May be dangerous as current may still be flowing through it

Neutral-Blue- 0V and completes the circuit

Earth- Green/ Yellow- 0V and only carries current if there is a fault in the plug. Safety wire to stop appliance becoming live. It is connected with earth and to the casing.

Question 7

Describe the shape of the graph when resistance is constant or not

Answer 7

Ohmic conductor- Current is directly proportional
Lamp- S shape
Diode- J shape

Question 8

Explain how LDRs and Thermistors work and 1 use

Answer 8

Light dependent resistors- As light intensity increases resistance decreases. 1 use is burgular alarms

Thermistors- As temperature increases resistance decreases. Are used in electric thermostats.

Question 9

What 5 factors affect resistance

Answer 9

Length
Light
Temperature
Voltage
Current

Question 10

Rules of current and resistance in series and parralell

Answer 10

Series-Current same everywhere
Resistance= R1+R2= R3

Parralell- Current splits into multiple paths
2 resistors in parallel will have a smaller overall resistance than just one