Electricity Flashcards
(25 cards)
What is the function of fuses?
It prevents the risk of fires and electric shocks
How to fuses work?
- If live touches metal case, then because the case is earthed, a big current flows thru LIVE WIRE, the CASE and EARTH WURE
- Surge in current MELTS fuse which cuts off LIVE SUPPLY
- this ISOLATES the whole appliance making it impossible to get electric shock from Case and prevents FIRE caused by heating effect of large current
How does earthing protect the device or user?
The case is attached to an Earth wire to reduce danger of electric shock.
An earthed conductor can never be live
How does double insulation protect the device or user?
- When appliance has plastic casing and no metal parts showing
- Plastic is insulator, so stops current flowing so you can’t get a shock.
- Anything with double insulation doesn’t need an Earth wire
Why are circuit breakers better than fuses?
- Easily reset by flicking a switch or pushing a button so they don’t need to be replaced
- Are able to react much faster
What’s the function and colour of the LIVE wire
BROWN
carries current to appliance at high voltage (around 230V)
What’s the colour and function of NEUTRAL wire
BLUE
completes circuit and carries current away from appliance
Nearly 0V
What’s the colour and function of the EARTH wire?
GREEN & YELLOW
Safety wire & connects metal case of appliance to Earth
Stops a fault making case live
What’s the difference between an AC and DC?
AC constantly switches direction in the circuit, but DC remains in 1 direction
Define CURRENT
RATE of flow of charge
What is the formula for charge?
Q = IT
Define potential difference
The amount of energy transferred per unit of charge passing through the terminals
what is the equation linking potential difference, energy transferred and charge?
V = E/Q
Define resistance
the opposition to current
Describe current in series
the same value at any point
- number of electrons per second that passes through one part of the circuit is the same number that passes through any other part
What does the amount of current in a circuit depend on?
- The voltage of the power source
- The number (and type) of components in the circuit
current in parallel
the current is conserved
In what direction does convectional current flow?
Positive to Negative
voltage in series
shared between the components
voltage in parallel
The potential difference across each component is the same
what are some advantages of a series circuit
- All of the components can be controlled by a single switch
2.Fewer wires are required
The disadvantages of a series circuit are…
1.The components cannot be controlled separately
- If one component breaks, they will all stop working as well
Advantages of parallel circuits
- The components can be individually controlled, using their own switches
- If one component breaks, then the others will continue to function
Disadvantages of parallel circuits
- Many more wires involved so much more complicated to set up
- All components have the same voltage as the supply, so harder to control if components need to have different voltages
