Safe Electricals Flashcards
To reduce smoke particles in chimneys, dust precipitators are used
How do they work
Metal plates and grids are at high voltage (potential difference) dust passes through grid and is charged
Dust particles now attracted to earthed plates, forming clumps
Large particles fall back down chimney when heavy enough or when plate is struck
How are electrostatics used for spray painting a car
Paint gun negatively charged
Paint particles negatively charged so they repel and spread out evenly
Car metal is positively charged by removing electrons so paint is attracted and sticks evenly
The car is then neutral🚗
What are positives of using electrostatics for spraying cars
Less paint wasted with fine and even spray applied
Even shadows of object receive coat of paint🎨
What is resistance
What is it measured in
Measure of how hard it is to get current through a component in a circuit at a voltage (potential difference)
Measured in ohms
How many volts/hertz does mains electricity use
230v / 50 hz
Will current increase or reduce by adding more bulbs to a circuit
Uses more electrcial energy
Current reduces
Is it easier for electricity to flow through a wire with low or high resistance
Low
Current in a circuit can be controlled by varying the resistance
How can this be done
Fixed resistor- resistance is constant. Higher resistance gives less current
Longer resistance wire- less current for voltage
Thinner resistance wire- less current for voltage
Variable resistor (rheostat) can alter resistance
What increases when voltage increases (and vice versa)
Current increases when voltage increases
For a fixed voltage what decreases as resistance increases
(and vice versa)
Current increases as resistance decreases
In a plug what is the brown wire
Explain it
Brown wire is live
Carries current to appliance at high voltage
Fuse, circuit breakers and switches part of circuit
carries high voltage
In a plug what is the blue wire
Explain it
Blue wire is neutral
Completes circuit
Carries current away from appliance
In a plug what is the green/yellow wire
Explain it
Green/yellow wire is earth
Safety wire stopping appliance becoming live
Fuse
For safety blows if current is too high
Current rating of the fuse must be just above normal current flowing through appliance
Has to be replaced
Circuit breaker
If current is too large the circuit breaker (electromagnet) pulls switch that breaks circuit and switches off current
For safety, can also be reset
