Electricity

Question 1

Household electricity

• direct current (examples)?
• alternating current?
• mains supply = a.c/d.c? = frequency? + voltage?
• how can u rectify a.c?
• PLUGS!!
• if electrical fault means too great a current flows then…..?
• what happens when current exceeds fuse rating?
• what are rccbs?
• appliances with metal cases are usually…..?
• which items together protect the wiring of the circuit?

Answer 1

• dc= current in same direction (cells and batteries)
• ac= in two directions (constantly changing)
• mains= ac = 50cycles per second = 230V
• using a diode
• circuit is disconnected by a fuse or circuit breaker in the live wire
• fuse melts
• = detect difference in current between Live and neutral wires
• earthed (some are double insulated)
• earth wire and fuse

Question 2

Electrical circuits

• what is electric current?
• materials that charges can move easily through?
• equation for current?
• equation for potential difference?
• SYMBOLS!!
• resistance can be found by….?
• greater resistance the …… the current for a given voltage across the component?
• resistance equation?

Answer 2

• current = flow of electric charge
• easily through conductors of electricity- eg metals
• current= charge/ time
• potential difference= energy/ charge
• by measuring the current through and potential difference across the component
• the smaller the current
• voltage= current x resistance

Question 3

Transferring electrical energy

• power=?
• equation for power?
• equation for power and voltage?
• energy transferred equation?
• electrical appliances are designed to…?
• amount of energy an appliance transfers depends on…? (2 things)

Answer 3

• power= energy/time
• power= current x voltage
• energy= voltage x charge
• designed to bring about energy transfers
• = how long it’s switched on for + its power

Question 4

National grid

• electricity along national grid from….?
• for a given power, increasing voltage =? (For current required and energy losses)
• what are used to change voltages in the national grid?

Answer 4

• power stations
• reduces current required + reduces energy losses
• step up and step down transformers