Electricity Flashcards
What are the two ways of joining electrical components?
In series and in parallel
What are the characteristics of components connected in series?
Same current through each component
Total potential difference is shared
Total resistance is the sum of individual resistances
What are the characteristics of components connected in parallel?
Same potential difference across each component
Total current is the sum of individual currents
Total resistance = 1/R_1 + 1/R_2…
What is the formula for total resistance in series?
R_total = R_1 + R_2…
What type of electricity is mains electricity?
Alternating current (a.c.)
What is the frequency of mains electricity in the UK?
50 Hz
Why does adding resistors in parallel decrease total resistance?
More paths for current reduce total resistance
What calculations can you perform in DC series circuits?
Currents
Potential differences
Resistances
What is the voltage of mains electricity in the UK?
About 230 V
What is the design and use of DC circuits for?
Testing purposes
What is the difference between direct and alternating potential difference?
Direct is constant; alternating varies over time
What are the three wires in a three-core cable and their colors?
Live wire: brown
Neutral wire: blue
Earth wire: green and yellow stripes
What is the function of the neutral wire?
It completes the circuit
What is the purpose of the earth wire?
To prevent appliances from becoming live
What is the potential difference between the live wire and earth?
About 230 V
What is the voltage within the neutral wire?
At or close to earth potential (0 V)
Why can a live wire be dangerous even when a switch is open?
It still carries potential difference
What are the dangers of a connection between the live wire and earth?
It can cause electric shock or fire
How do domestic appliances transfer energy to a motor/ kettle?
From batteries or a.c. mains
To kinetic energy of motors
To energy of heating devices
What is the National Grid?
A system of cables and transformers
Links power stations to consumers
How is electrical power transferred to consumers?
Using the National Grid
What is the role of step-up and step-down transformers in the National Grid?
Step-up: increase potential difference for transmission
Step-down: decrease potential difference for domestic use
Why is the National Grid an efficient way to transfer energy?
It minimizes energy loss during transmission
What risks are associated with electric shocks?
Electrical interference with heart/ pacemaker
Burns
